A Simple Trigger is a type of trigger that usually does not have any unique paramteters and rarely has any parameter requirements. These are generally the easiest to use "as is".

The 24 simple triggers are acidrain, adventure, blizzard, bloodmoon, bluemoon, cloudy, creative, dead, drowning, elytra, fishing, harvestmoon, home, hurricane, lightrain, lowhp, pet, raining, sandstorm, snowing, spectator, starshower, storming, and underwater.