Poke-Power Cards are cards that can help your Pokemon in battle.There are many kinds such as the Smoke Card that reduces your opponent's sight and evasiveness and the Speed Card that boosts your Pokemon's speed.
Some cards are for a certain type, like the Inferno Cards that enhance fire Pokemon's power and moves.
Other cards can give your Pokemon armor and different items to mix up the battle.
A trainer can own up to 4 cards for now.They also must be fair. In order to use a Card you must say the name of the card proceded by 'activate!'.So for example, if you used the Smoke Card you would say, 'Smoke Card, Activate!'.
There are EXTREMELY unique cards that can even make your Pokemon evolve just for the battle!
Your Pokemon have their own unique card, only other cards are for the majority.