Twitch is a website created for the purpose of sharing live video feeds (called "livestreams" or just "streams") on the Internet. Initially intended for a variety of generic uses as Justin TV, Twitch's current incarnation focuses almost entirely on video gaming.
Twitch's primary purpose is to allow users to record themselves playing video games while others can watch in real-time as they play the game. The service has frequently seen use in high-profile eSports events as to allow interested viewers to spectate games or matches that they ordinarily cannot see live; outside of this, Twitch has also seen use by casual players in order to merely record themselves playing for a public audience, including Let's Plays. Applied uses of Twitch have allowed for viewers to interact with streams, as seen with "Twitch Plays Pokémon", and for viewers to bet on streams, as seen with "Salty Bet".
Streams recorded in Twitch can also be uploaded to YouTube upon their conclusion; similar to YouTube, Twitch also offers a partnership program that allows users to potentially monetize their streams.
Relevance to the Super Smash Bros. series
Given little attention early in its lifetime, Twitch has since become a seriously important aspect of competitive Smash. Tournaments have made use of the site's services in order to allow outside viewers to watch live matches, an action that previous sites could not easily perform. The site's ability to upload streams to YouTube also allows for those who have missed specific matches to view them later. Organizations such as VGBootCamp, 2GG, MVG, and many others use Twitch to stream a plethora of regional to national-level tournaments. Nationals typically see thousands of stream viewers throughout the event depending on the Smash game. EVO, considered the most prestigious fighting game tournament, brings in hundreds of thousands of viewers at a time for Smash. The growth of the community can be heavily attributed to the widespread use of Twitch for streaming Smash events to a grand total of possibly millions.
Outside of its use in tournaments, many high-level smashers have streamed casual friendlies and money matches with the site's services to general viewers as to show how they play the game regardless of whether or not a tournament is occurring.
Twitch also became popular with the Japanese release of Super Smash Bros. for Nintendo 3DS; multiple players residing in Japan streamed live footage of the game to prospective Western players in order to show off multiple unlockables in the game, as well as give demonstrations of the general gameplay.
Use by Nintendo
Nintendo itself owns a Twitch stream, under the name of "Nintendo". Nintendo's Twitch channel is intended to showcase various trailers of games at specific times and specific events, notably for Nintendo Direct and E3, along with others.
Problems with Project M
Owing to Project M falling into a legal gray area as a mod, some difficulties with streaming Project M have occurred on Twitch. Many monetized streams have been unable to stream Project M due to this legal gray area, and as a result, many streams from tournaments and similar venues have had to move instead to hitbox.tv in order to stream the game.
Notable smashers working for Twitch