Poke-Bodies are always active, they are a contious ability which can be used on the active or bench.
Poke-Powers are a Pokemon effect that must be declared and activated by the player. It may require the Pokemon to be in the Active Pokemon spot or on the bench or both. Some Pokemon have a poke-power when they are evolved.
Here are some examples.

Regular Poke-power/ability:


Evolution Ability:


Active Pokemon ability:


Then you have poke-bodies which will normally work on the bench and active spot.