I've begun figuring out what all the various .entity files do, for reference to ease making new ones that fit my uses. This is by no means a perfect list, but I think it would help a lot of people. If something is wrong, please correct me, if something is marked with a ? at all it means I was either confused as to what it does and guessed or didn't even guess.
Buffs
BuffAbilityGuidance - Cooldown rate
BuffAdaptiveShield - Reduces chance to ignore shields
BuffAntiMatterDetonate - DoT, drains AM and does damage
BuffAntiMatterRechargeModule - BoT, restores AM
BuffAntiMatterRestore - Instantly restores amount of AM
BuffAsteroidBelt - Reduces chance to hit?
BuffBattleMeditationChild - Increases damage dealt by percent
BuffBattleMeditationParent - Applies above to fighters
BuffBattleMeditationSelf - Applies above to all ships in range capable of having fighters/and are psi
BuffBeamBlastActivated - Fires Beam weapon at the enemy
BuffBeamBlastCharging - Precursor to above; can be interrupted
BuffBeamBlastDamage - Damage affect for the beam weapon
BuffBlackout - Interrupts enemies: forces retarget and chance for caster to not be targeted; disables: abilities, construction, phase jump, engines, regen, weapons for a period of time or damage taken.
BuffBonusModuleDamageSelf - Lowers cooldown on planet bombing; applies extra damage to target
BuffBonusModuleDamageTarget - The extra damage
BuffBoostMorale - Restores shields, weapon cooldown, for a period of time
BuffBoostResourceExtractionOnShips - Disables Phase jumps and engines?
BuffBoostResourceExtractionOnSelf - Applies above to linked cargo ships?
BuffCannonShellPhaseOnShips - Damages an enemy, disables engines, jump, weapons, regen for a period of time
BuffCannonShellPhaseOnStructures - Same as above but on structures, disables structure abilities
BuffCannonShellPhaseSpawn - Trigger for above damage; Hits planet modules within range, hits all enemy ships within range
BuffCannonShellPsi - Calls next on friendly ships in the area, applies CultureSpread
BuffCannonShellPsiOnShips - Increases damage dealt by 15%
BuffCannonShellTech - Damages planet/population
BuffCaptureNeutralEntity - ?
BuffCeaseFireSpawner - Affects enemy and friendly ships in range with next
BuffCeaseFireTarget - Can not be damaged, disables weapons and abilities (ultimate?)
BuffChargedMissilesDoDamage - applies damage
BuffChargedMissilesLightDoDamage - applies damage
BuffChargedMissilesLightSelf - Fires on enemy fighter and calls above; disables engines and increases weapon range
BuffChargedMissilesLightSpawnDamage - Calls damage on fighters in range
BuffChargedMissilesSelf - Calls next on enemy ships/structures, disables engines, loss of angular thrust, weapon range increase
BuffChargedMissilesSpawnDamage - Calls damage buff on enemy ships within range
BuffCloneFrigate - Creates clone frigates
BuffClusterWarheadsDoDamage - applies damage
BuffClusterWarheadsSelf - calls damage Buff for enemy target
BuffClusterWarheadsSpawnDamage - calls damage for enemy ships within range
BuffCrippleAbilities - Increases ability cooldown rate, increases AM cost
BuffDamageOverTimeAuraSpawner - Calls damage buff on enemy objects in range at intervals
BuffDamageOverTimeAuraTarget - spplies damage
BuffDefeatShields - Decreases shield mitigation, increases chance to ignore shields for period of time
BuffDesignateTargetCaster - Calls designate target buff for period of time
BuffDesignateTargetOnTarget - Increases damage on target by 25%
BuffDetectPhaseJump - Detects incoming entities
BuffDetectPhaseJumpModuleOnPlanet - ?
BuffDetectPhaseJumpModuleOnSpawner - Continuously calls above for finish conditions?
BuffDisableImmuneCaster - Calls next on target for period of time
BuffDisableImmuneTarget - Increases Hull restore rate, Immune to non ultimate disables
BuffDisintegrationBounceBack - Instantly restores some hull
BuffDisintegrationCharging - Calls next for period of time
BuffDisintegrationSelf - Beam weapon, does DoT for period of time and calls next
BuffDisintegrationTarget - appears to send back to caster the bounceback buff over time
BuffDisruptiveStrikesSelf - Fires weapon at enemy w/ AM
BuffDisruptiveStrikesTarget - Removes some anti-matter, increases ability cooldown rate
BuffDomination - ?
BuffEmbargoPlanet - steals production over time, increases ship build time/module build time
BuffEmbargoSelf - Calls above and calls next on enemy cargo ships
BuffEmbargoShips - Disables Phase Jump
BuffEMPBlastAction - applies damage and removes AM
BuffEMPBlastSpawn - Calls above on enemies within range
BuffEnergyAbsorb - Percentage of damage to AM, increases armor as damage target
BuffEnergyWeaponBoost - Decreases Energy weapon cooldown
BuffEnergyWeaponBoostSelf - Applies above to targets within range at intervals
BuffEvasiveManeuvers - decreases chance to be hit for period of time
BuffFarSight - Increases sight range for period of time
BuffFighterBlinkActive - Teleports toward target specific range
BuffFighterBlinkTrigger - Periodically checks for the chance to activate above
BuffFinalAttackActivate - Applies next, Makes target dead, matches velocity
BuffFinalAttackOnTarget - Applies damage
BuffFlakBurst - applies damage
BuffGaussBlast - applies damage
BuffGravityFieldCaster - periodically applies next to enemies within range for a period of time
BuffGravityFieldTarget - Slows targets
BuffGravityWarheadAction - slows targets for a period of time
BuffGravityWarheadSpawn - applies above to enemy targets within range
BuffHeavyFighters - Increases damage dealt, increases armor as damage target
BuffHyperspaceDisruptionSpawner - Periodically applies next to targets within range
BuffHyperspaceDisruptionTarget - reduces charge up rate for HS
BuffIllusionSelfCopyOnClone - Modifiers for illusion ships
BuffIllusionSelfCopyOnSelf - Creates copies and gives them above; forces retarget; increases chance caster will not be targeted
BuffIncendiaryShellsSelf - Applies next to targets on weapon fire
BuffIncendiaryShellsTarget - Adds damage over time
BuffInstantBuildFightersSpawner - Periodically calls next for period of time
BuffInstantBuildFightersTarget - Decreases ship build time/module build time
BuffIonBlast - applies disable: abilities, construction, modules, phase jump, engines, regen, weapons for a period of time
BuffIonBurst - Applies disable: "" for a longer period of time
BuffLastStandDoDamage - applies damage
BuffLastStandSelf - On weapon fire calls next; restores AM/hull/ability over time
BuffLastStandSpawnDamage - Calls dodamage on enemy targets within range
BuffLowCostAbilitiesSelf - Periodically calls next on friendlies within range for a period of time
BuffLowCostAbilitiesTarget - Decreases AM cost
BuffMagneticCloud - disables ultimate abilities
BuffMagnetize - Magnetizes enemy fighters in range; I believe it pulls them toward you, damaging on impact?
BuffMissileBarrageFiring - periodically calls next on enemies within range for a set number of times
BuffMissileBarrageHit - applies damage
BuffMissilePhaseBoost - Increases chance to ignore shields
BuffNanoDisassembler - applies DoT on hull, bypasses armor for a period of time
BuffNanoDisruptorAction - applies instant damage
BuffNanoDisruptorSpawn - Calls above on enemies within range
BuffNanoHullRepairAction - increases hull restore rate for a period of time
BuffNanoHullRepairSpawn - Calls above on friendlies within range
BuffNeutralCapturableEntity - modifiers for neutral capturable entities
BuffPhaseCloak - Drains AM over time; applies disable: phase jump, engines, regen, weapons; phases out, cannot be damaged
BuffPhaseGateCapitalSpawnerCaster - applies next to any planet/star for period of time
BuffPhaseGateCapitalTarget - modifies entity to become phasegate end point
BuffPhaseGateModuleSpawnerCaster - calls next on planet
BuffPhaseGateModuleTarget - modifies planet to become phase gate end point
BuffPhaseMissileSwarm - applies damage
BuffPhaseModuleConstruction - calls next on target; increases buildrate
BuffPhaseModuleConstructionTarget - Increases construction rate
BuffPhaseOrbitalCannon - unsure
BuffPhaseOutHull - applies phase out modifiers
BuffPlanetConstructionBoost- decreases module build times for a period of time
BuffPlanetCripple - decreases resource output, increases build times
BuffPlanetManiaActivated - damage planet/pop over time
BuffPlanetManiaCharging - charges planet mania
BuffPlanetManiaOnPlanet - applies effect on planet
BuffPlanetShieldOnPlanet - Increases absorption of planet bombing damage
BuffPlanetShieldOnSpawner - Periodically applies above to planet
BuffPlasmaStorm - Disables fighter launch
BuffPowerSurge - decreases weapon cooldown, increases shield restore
BuffProbe - gives proxysensor modifier
BuffProtectedShutdown - Decreases damage taken, phases out, disables construction/module functionality
BuffPsiCapitalColonize - decreases planet upgrade cost for period of time
BuffPsiCommand - increases fighters per squadron
BuffPsiModuleConstruction - applies next; bulidrate increases
BuffPsiModuleConstructionTarget - increases under construction rate
BuffPsiOrbitalCannon - attaches charge and muzzle effects
BuffRadiationBombDamage - applies DoT
BuffRadiationBombSpreader - applies damage, periodically applies above to enemies within range
BuffRazePlanetLauncher - Periodically applies next
BuffRazePlanetTarget - applies damage/population
BuffReactiveNaniteArmor - restores hull points
BuffReactiveNaniteArmorBuff - adds to max hull, increases armor
BuffRecentlyColonized - applies effects
BuffReinforcedArmor - Restores hull points, increases armor, increases max hull points
BuffRepairDroids - Restores hull over time
BuffRepairPlatformPhase - Increases Hull restore rate
BuffRepairPlatformPsi - increases hull restore rate
BuffRepairPlatformTech - increases hull restore rate
BuffRepulsionFieldCaster - periodically applies next to enemy ships within range; drains self AM
BuffRepulsionFieldTarget - decreases thrust/maxspeed; repulses enemy from caster
BuffResourceDrainActivated - damage and pop over time, increases resource rate
BuffResourceDrainCharging - Charges resource drain
BuffResurrection - applies resurrection effect; resurrects cap ship
BuffRevengeBounty - adds bounty amount when player dies?
BuffSabotageAntiMatterPostCast - Disables abilities
BuffSabotageAntiMatterPreCast - applies damage; calls postcast
BuffSabotageEngines - calls next
BuffSabotageEnginesSlow - applies damage; decreases thrust/maxspeed; disables weapons
BuffSelfRepairHeavy - Increases hull restore rate; disables engines/weapons
BuffSelfRepairLight - same as above
BuffShieldProjectionCaster - Periodically calls next on friendlies within range
BuffShieldProjectionTarget - Shares damage with caster
BuffShieldRegenerateCaster - Periodically applies next to friendlies within range
BuffShieldRegenerateTarget - increases shield restore rate
BuffShieldRestoreActivate - Fires beam through shields, calls next
BuffShieldRestoreOnTarget - Restores amount of shield points
BuffShipCrippleSpawner - Calls next on enemy ships within range
BuffShipCrippleTarget - increases weapon cooldown, decreases chance to hit
BuffSlowEnemyHyperspaceCaster - periodically applies next to enemies inbound
BuffSlowEnemyHyperspaceTarget - reduces hyperspace speed
BuffSlowPopulationGrowthSelf - applies next to enemy planets; increases chance to hit
BuffSlowPopulationGrowthTarget - slows pop growth
BuffSolarCloaking - adds effect
BuffSolarRegeneration - increases AM restore rate
BuffSpeedBoost - increases speed, decreases gravitywell range for entering hyperspace
BuffSpeedBoostSelf - applies above to friendly targets within range; immune to jump blocker
BuffSpeedBuildModuleSelf - applies next to target; increases bulidrate and decreases module cost
BuffSpeedBuildModuleTarget - increases construction rate
BuffSpreadWeaponDamageSpawn - applies next to enemies within range
BuffSpreadWeaponDamageTarget - Spreads damage among enemy ships in range of damage taker
BuffSprint - increases speed
BuffSpyingAttacksSelf - applies next to target planet/star
BuffSpyingAttacksTarget - gives proxysensor modifier
BuffStealAntiMatter - Steals amount of AM
BuffStealResourcesSelf - applies next to target
BuffStealResourcesTarget - steals amount of credits
I will finish this list tomorrow