Pokémon is a highly successful Japanese franchise that was introduced in the 1990s. Owned by Nintendo, it has risen to become the second most successful video game franchise, behind Nintendo's own Mario. It spread to several other countries in a short time.
The series focuses on capturing, training, battling, collecting and trading various monster species, known as Pokémon. While the mechanics vary from incarnation to incarnation, the player generally takes on the role of a Pokémon trainer, seeking to capture wild monsters, raise them, and defeat other trainers in duels using the captured monsters in order to become a champion.
In Japan, Pokémon is referred to as Pocket Monsters. The name was changed in North America due to another franchise called Monster In My Pocket. Pokémon is a romanization of Pocket Monster.
Pokémon was originally released in Japan in 1996 as a pair of cartridges, Pocket Monsters Red and Pocket Monsters Green, for the original Game Boy system. Three years later, the games were released as Pokémon Red and Pokémon Blue in the United States and worldwide. The games feature similar gameplay, differing primarily in what monsters are available in each version. New versions of the game are released periodically, normally in pairs, to introduce new monsters and to take advantage of improving hardware technology. As of the release of Pokémon X' and Pokémon Y in 2013, there are 719 species of Pokémon available.
Players take the role of a Pokémon trainer, seeking to capture wild Pokémon with "Pokéballs", small spheres in which captured creatures live. In each game (excluding Pokemon Yellow), the trainer begins by selecting one of three "starter Pokemon" that are either grass, fire, or water types. These Pokemon each evolve twice. The player travels across the region challenging other trainers while raising their own Pokémon and capturing new ones. The games normally feature a sub-plot where the player, with the help of their Pokémon, foil the schemes of a criminal organization or terrorist group. The player must also challenge eight advanced trainers known as "gym leaders" before they can challenge the "Elite Four" and the "League Champion", five of the strongest trainers in the region. The games also challenge the player to see and capture as many species as possible. However, this is made difficult due to different game versions having exclusive Pokémon, requiring the player to trade with other people who have the opposite game version. Certain Pokemon deemed "legendary" have power far superior to other Pokemon, and only appear once in each game. Some Pokemon are only given in Nintendo-held events, and while most of these events give away legendary Pokémon that cannot be obtained otherwise, there are many exceptions.
In a battle with a wild Pokémon or a match against a trainer, the player's Pokémon and the foe alternate using up to four learned moves, with the ultimate goal being to knock out all of the opponent's Pokemon. If the player encounters a wild Pokémon, they can choose to attempt to capture it or run away, rather than knocking it out. Players cannot run-away from a trainer battle. A captured Pokémon joins the player, and this is the entire premise behind the series. However, this is not the only way a trainer can have Pokémon on his team. Pokemon can be given by in-game events (such as Eevee in the original games), an in-game trade (such as Mr.Mime) or can be hatched from an egg. Pokémon can also be bred, in specialized day care centers.
Originally, Pokemon could be classified in one or two of 15 types. This number was expanded to 17 in Generation II. This is later increased in Generation VI to 18 with the introduction of the fairy type. Pokémon moves are further subdivided into physical and special moves each of which is controlled by a specialized attack and defense stat. Prior to the introduction of Generation IV, this split was originally based upon the moves type; however in Generation IV it became based upon developer designation. Most moves are mono-type; however, Generation VI introduced a dual type move, which deals different damage, than a move of its two constituent types.
Many Pokémon, with sufficient training, will spontaneously change form, developing into a larger, stronger species. This process is called "evolution", though it more closely resembles growing up and maturing, or the metamorphosis of insects, and has little to nothing to do with the Theory of Evolution. Many Pokémon species can evolve multiple times, and many species can only be obtained by evolving more basic ones. In addition, some Pokemon can evolve in more than one different path instead of the linear evolutionary path most Pokemon take, and a good number of Pokemon have gained the ability to evolve in a game after their introduction. Generation VI introduced a special form of evolution called "Mega Evolution". In order to "Mega evolve" a Pokemon must be holding its respective "Mega stone". This process typically results in the increase in all of the Pokemon's stats other than HP. Some stats may be lowered, such as in the case of Mega Garchomp, which suffers a drop in speed, in exchange for a large increase ,in most of its other stats. However,there are restriction on this, Players can only have a single Mega- volved Pokemon on their team at a time and the Pokemon also loses the ability to hold other items, which may be more useful due to certain effects such as healing. This restriction , however, is not held by Mega Rayquaza, which only has to know a certain move to Mega Evolve. Players may also breed their Pokémon with each other by leaving them in a daycare, where the player can eventually obtain an egg. Eggs eventually hatch into Pokémon, giving the player another option for acquiring new Pokémon.
Additionally, other video games featuring the Pokémon characters have been released, including Pokémon Pinball and the Pokémon Ranger series.
The Pokémon video game franchise has been adapted into various other media. In 1997, it was adapted into a cartoon show for children which follows the adventures of Ash Ketchum and his friends, as well as their Pokémon. The program is notable for an episode aired only in Japan in which flashing lights caused by one monster's attack induced seizures in hundreds of viewers. Several films based on the series have been produced and released worldwide. 
The franchise also spawned a collectible "trading card game", where players duel using special decks consisting of cards representing different Pokémon species, as well as energy cards, which allow Pokémon to use their battle techniques, and trainer cards, which have special effects that influence the flow of battle. The game uses mechanics adapted from the video game, and features characters from the video game and from the cartoon.
- Pokemon.com (English) (HTML). The Official Pokémon Website.
- Pokemon.com, The Official Pokémon Website 
- The New York Times; TV Cartoon's Flashes Send 700 Japanese Into Seizures
- Go-Pokemon.com (English) (HTML). The Official Pokémon TCG and OP Website.