The Filter properties of an actor determine the conditions under which the actor will be present in gameplay.
In SinglePlayer, there are four difficulty levels that can be applied. In Unreal, they are called Easy, Medium, Hard, and Unreal. The default difficulty level is Medium. The contents of these variables is used to determine which difficulty levels the actor should be present or absent in.
If True, then this actor will appear in regular network play.
If True, then this actor will appear in special network play mode.
If True, then this actor will appear in standalone gametypes.
In a game where this actor would normally exist, this value (between 0 and 1.0) determines the probability of the actor actually appearing. For most actors, this value is equal to 1, which means that the actor will always exist in relevant games.