Entity Filters are used at a few locations in PneumaticCraft. They all work the same. In a text box you can specify which Entities to include. It works as follows: To specify certain Entities, whether they are of the same type ('Creepers') or have the same name (a player called 'MineMaarten'), just put it in by plain name. When you want to specify a certain entity type (animals, aggresive mobs, players in general), you put a '@' in front. Here are all the '@' types, and usage examples:

@player --> allows all players only
@mob --> allows all aggressive creatures only
@animal --> allows all passive creatures only
@animal(age = adult) --> allows all passive creatures that are adult only
@animal(age = baby) --> allows all passive creatures that are baby only
@animal(breedable = yes) --> allows all passive creatures that can breed at this very moment (they'll consume wheat/carrots/...)
@minecart --> allows minecarts only
@living --> allows all living entities only
@item --> allows item entities only
@drone --> allows drone entities only
Creeper --> allows Creepers only
MineMaarten --> allows MineMaarten only
c* --> allows any entity starting with the letter 'c' only (like Creepers, or Cows).
*pig* --> allows any entity that includes 'pig' in the name only (like a Pig or Zombie Pigman).