Power is the DEC burn value and Collection Power value of your card. As the power level of your card increases, BCX (Base Card Experience) must also increase. Overall, the more power your card has, the stronger it is and the more copies have been combined into it. Navigate to the card details screen via the Items or Shop page to view the power of a specific card.
Note: Reward cards come with different amounts of power depending on when they were released. You can recognize the different types of Reward cards by their border.
As you combine cards the power of the cards will also combine.
As you can see in the tables, gold foil cards give at least 25 times more power. They also let you earn more Reward/Season/Focus Points and SPS.
Use Peakmonsters to view your full Collection Power and your cards in a variety of ways.