The link's broken on the other answer, so here is an updated one: The Link
In case you don't like links, and so my answer has actual content, here is a general basic description of how to play the Pokémon TCG.
In the TCG, you have cards. (Obviously) You make a deck with these cards, before you play. There are three main types of cards:
- Pokémon cards
- Energy cards
- Trainer cards
Your Pokémon cards are your Pokémon. they attack your opponent's Pokémon. However, they need energy attached to attack. That's where the energy cards come in. You attach the energy cards to your Pokémon to let them attack. Trainer cards can help you in many different ways, but the point is that Trainer cards are there to support you Pokémon cards, in some way.
You also have prize cards. At the beginning of the game, you put out six cards, facing down. each time you KO one of your opponent's Pokémon, you take a prize card. When you take all your prize cards, you win.
This is just a very simple explanation of how to play the Pokémon TCG. For more detailed information, go to the link at the beginning of this answer. Hope I helped.
Source: The link I linked you.