The World Series of Football (aka WSOF) is a friendly club tournament held during the summer in the USA by MLS clubs. This competition gives big European and international clubs a chance to prepare for their upcoming seasons and a chance to grow their fanbase in the USA, while MLS clubs benefit by having the rare opportunity to sharpen their skills versus high calibre international opponents as well as lucrative fixtures.
This tournament seems to replace the privately promoted ChampionsWorld Series which began in 2003 with top clubs and than ballooned to a bloated 9 club, 11-game North American tour, with high priced tickets, duplicate venues and huge hosting costs upwards of $30 million, eventually leading to the promoter's bankruptcy in 2005.