The FIFA World Cup is the world championship for national soccer teams and occurs once every 4 years. Professional soccer players play in two settings; club and national. Well known club teams include F.C. Barcelona and Manchester United. Clubs do not participate in the World Cup. Instead, 32 nations from 6 regions around the world qualify after battling the other teams in their regions for two years.
Players from these nations must be selected to represent their country in the qualifier matches. Often, countries maintain national player pools with hundreds of potential players. In the end, the national team coach for sides that qualify may select only 23 players to the squad that travels to the World Cup. Selection is prestigious and, potentially, lucrative.
The 32 teams that qualify for the World Cup finals are drawn into 8 groups of 4 teams each. In the Group Stage, the 4 teams in each of the 8 groups play a round robin format. The top 2 teams from each group advance to the "knockout" stage. In the "knockout" stage, the remaining 16 teams are drawn into a bracket and play single-elimination games until one team emerges as champion.
The World Cup is the planet's most watched sporting event. It is estimated that the 2010 World Cup will have a cumulative viewership of 30 billion.