A pokémon needs to have "energy" to do their moves or to retreat. Each pokémon has HP (hit points) which is the # oh health they have. Every time a pokémon gets 10 damage off of them, you place a "damage counter" on that pokémon so everyone knows it has 10 damage off.
There are also other cards called "Trainer Cards" these are one time cards which can do numerous amounts of things like: heal pokémon, draw cards, +damage, +health, etc...
There are 3 ways you can win:
1: Every time you kill your opponent's pokémon, you can pick up one your prizes. Once you have no more prizes left, you win!
2: If your opponent has no more "benched" pokémon after you kill his/her active pokémon, you win!
3: If your opponent has no more cards in his/her deck after their next turn, you win!
There is much more about the game that I have not said. So why don't ya go out and pick yourself up a deck with a rule book, chansey coin, and damage counters so you can learn more about the Pokémon TCG!