Ents
From GMod Wiki
ents is the entities library. This is probably one of the most important libraries in Gmod Lua, as it allows scripts to create entities, find entities, etc. (If it vanished, right now, you wouldn't spawn at "info_player_start" and many popular gamemodes would be broken)
Library Functions
ents.FindByName
ents.FindByModel
ents.Create
ents.FindByClass
ents.FindInBox
ents.FindInCone
ents.FindInSphere
ents.GetAll
ents.GetByIndex