Pokémon (Full name Pocket Monsters but no-one cares about that) is a multimedia franchise made by Nintendo that for a fair amount of the late 90s and part of the early 2000s was more popular then God, Haribo and Cadbury chocolate combined. Using a bunch of pocket monsters (whose primary weapon against the fanbase was an almost illegal level of cuteness) you would battle another trainer with his own little monsters until yours made his faint and you'd win the game!
It started off as a game where you would journey around the world and "try to catch 'em all" (the 'cool' catchphrase of the series). Through a combination of the aforementioned charm, ability to raise your own poke-pets in the game, the surprisingly deep strategic elements, and the drugs they put in the cartridges it quickly became an addiction and spawned a whole host of sequels, a trading card game, several comics, a TV series, and a bunch of movies. Nowadays trying to "catch 'em all" is something best left for people with OCD, as there are well over 700 Pokémon in existence. It's not as wildly popular it used to be, but it's still got quite a large fanbase, especially in Japan.
If you have any further questions about the video games, go to /vp/. Yes, 4chan has an entire board dedicated to Pokémon, why do you ask?
The Pokémon TCG is a collectible card game based on the existing video games. It was originally released in 1998 by Wizards of the Coast during the great "Pokémon Craze" associated with the release of the original games and TV show when they started in Japan and then broke out of Asia into the west. Once wildly popular, it has declined over the years. It is still quite fun and funny if you can find friends to play it with. If you can't get over the fact that it's Pokémon-themed, I pity you... although it's highly unlikely you have friends that can get over the fact that it's Pokémon-themed, so... never mind.
What are Pokemon?
Pokemon are various brightly colour'd anime creatures that resemble real world animals, birds, sea creatures, plants, mythical beings, and even inanimate objects, often with an added elemental theme (for example Charmander, a fire type lizard pokemon, has bright red skin and a tail with it's tip constantly alight).
Each Pokemon species has a name that is often a pun on what it is or looks like and will have a variety of powerful abilities to use.
Pokemon are often described as friendly and eager to battle to test out their abilities, which is perfect for trainers as they don't have to try to force their Pokemon into battling then; they are all eager for it themselves!
How to play
At the beginning of the match both players shuffle their decks (of exactly 60 cards) and draw 7 cards as a hand. They then put the top six cards of the deck face down as "Prizes." The players can put down any basic Pokémon they have in their hand in front of them face down, and any extra basic Pokémon they have behind that Pokemon on the "Bench", also face down. Players must play basic Pokémon on their setup phase. If they don't draw one in the first seven cards, they show their hand to their opponents, shuffle again (without the prizes) and draw 7 new cards. The opposing player may draw two additional cards if he wants to. There is no max hand size. Players flip a coin to decide who goes first. The cards are then flipped face up.
Every turn follows this basic course:
1. choose a card facing up
2. Play basic Pokémon and/or evolve Pokémon and/or play trainer cards and/or attach one energy card and/or use Pokemon Powers and/or retreat Pokémon and switch in benched ones
3. Attack with active Pokémon
4. End of turn
Pokémon need energy to attack. The energy is not discarded when using an attack, except when the attack says so (see the card on the top of the page for an example). If a Pokémon deals damage its always in 10-damage-steps. Indicate those with markers on the card. If an attack connects look at the bottom left corner of the defending Pokémon. If it has a weakness against your type (which is shown on the upper right corner of your card) the damage you deal is doubled. If it has a resistance against your type the damage will be reduced by 20 points. (Up to 0 points of damage. You won't heal the defending Pokémon.) On the upper right corner of the card is the HP of the Pokémon. If the damage counters on the card match or exceed these it is defeated, goes to the discard pile and the owner of the Pokémon who defeated it takes one of his prizes.
Some cards are evolutions of basic Pokémon. They can only be played on the corresponding basic pokemon shown in the upper left corner. The attacks and powers of the basic pokemon are lost and only the evolution counts from now on. All damage counters remain on the pokemon but it is cured from any condition. You can't evolve a pokemon the turn you played it or on your first turn. This also counts for evolutions (You can't evolve a just evolved pokemon another step on the same turn). Evolutions can be played on any pokemon on your field, even benched ones. You may also evolve as many pokemon as you like in your turn as long as you don't violate the above rules.
Evolved pokemon do not have any restrictions! They can attack the same turn they evolved and you can even attack in your first turn.
Trainer cards may be played any time before your attack. They don't have any additional costs to the ones written on the card itself, if any. Trainer cards can have an effect on anything.
Bring back a basic Pokémon from your discard pile and put in play on your bench with half its HP in damage counters on it (rounded up) (Reviver)
Draw 2 cards (Bill)
Choose a benched pokemon of your opponent and switch it with his active Pokémon. (Gust of wind)
Flip a coin. If it heads choose any basic Pokémon or evolution card from your deck, reveal it and put it into your hand. (Poké Ball)
Discard an energy card attached to your active Pokémon. Then discard 2 energy cards attached to your opponents active Pokémon. (Super energy drain)
Energy cards come in 6 variations: Psychic, Fighting, Fire, Water, Electric, and Grass. Those + colorless are also the only types your Pokemon can have (Except some nonsensical ones made later into the game as the Pokemon franchise expanded. But we all know what the real Pokemon generation is.)
You can attach one energy card to any Pokémon on your turn and not more. You can also attach any energy card type to any Pokémon, even if that Pokémon can't use it. The energy cards will just have to match the conditions for the attacks in order to use them. If you attached 4 Fire energy and one Psychic energy to Charizard at the top of this page that is perfectly okay, but you will never actually be able to use the Psychic energy effectively. White stars indicate colorless energy. Even though there is a trainer card "Double Colorless Energy", you can meet the requirements for those attacks with any color. Dugtrio's Slash to your right here could be payed with 2 Fighting Energy + anything.
To retreat your active Pokemon and exchange it with a benched one you have to pay the retreat cost in the lower right corner. By paying I mean discard the energy attached to the Pokemon equal to the cost.
You should know the most by now. But in case you are an idiot and skipped reading the above I'll tell you again:
You can play basic pokemon to your bench. Your bench holds up to 5 pokemon. You can only evolve to higher level pokemon via the basic ones. You can not skip an evolution step. (Except with some trainer cards like Pokemon breeder). When your active pokemon bites the dust you have to switch to a benched one. No you can't play a basic pokemon from your hand when your active one jumps the line, it has to be benched beforehand.
Some pokemon have Pokemon Powers (Charizard at the top of this page has one for example). You can activate it on your turn before your attack as long as your pokemon is not asleep, confused or paralyzed. Some of them are just helpful (look at Venusaur to your right there.) and some are just outright unfair. Like Mr. Mime's Power. He can reduce any damage to him greater than 30 to 0. If you happen to be playing his weakness, you are fucked. Unless he's asleep, paralyze him or confuse him. Speaking of which...
Your pokemon can suffer one of four status conditions:
Poisoned: Indicated by a marker on the pokemon. Between every turn your pokemon gets 10 damage. Yes, even between the turn of your opponent who just poisoned your pokemon and your turn. You get no check to get rid of poison.
Asleep: Indicated by turning your card 90° counter-clockwise. Your pokemon can't attack or do anything else. between every turn it gets one check, meaning you trow a coin. If it's heads, your pokemon wakes up. If it tails, its still fast asleep.
Confused: Indicated by flipping your card 180°. If you want to attack or retreat you will have to flip a coin. If it heads, everything is fine. If it tails your retreat fails, or if it tried to attack it deals 20 damage to itself and the attack fails. You will have to pay for everything an attack or a retreat may want from you and THEN check if it fails or not. If your retreat or your attack fails you don't get another chance. You don't get a check to get rid of confusion.
Paralyzed: Indicated by flipping you card 90° clockwise. Your pokemon can't act in any way and is automatically healed at the end of your opponents turn. You can't retreat it either.
Poisoned goes with any of the other three, meaning you can be poisoned and asleep at the same time. Sleeping, paralysis, and confusion on the other hand cancel each other out as soon as the pokemon gets a new status. So you can only be sleeping or paralyzed or confused. (Highlighted for your incompetence.)
Losing the game
You lose the game by not being able to put a pokemon from your bench in the active zone when your active pokemon is defeated. Also, if you can't draw a card at your beginning step because you don't have any more. Notice: It only counts as a loss if you can't draw at the beginning of your turn. If your opponent somehow forces you to draw cards and you don't have as much cards in your deck anymore you just draw all cards and do not yet lose. You only lose at the beginning of your step. You also lose if your opponent draws all prizes before you do.
When both players win at the same time (Example: Your pokemon does an attack that damages itself. You defeat your opponents pokemon and your own is defeated by that self inflicted damage. Neither of you have any benched pokemon.) a sudden death will start. Shuffle your decks completely new and make a new game with just 1 prize. Everything else goes normal.
While no official Tabletop Game exists, /tg/ has been working on a homebrew system called Pokemon Tabletop Adventures.