In the United States, the most commonly played game is eight-ball. The goal of eight-ball, which is played with a full rack of fifteen balls and the cue ball, is to claim a suit (commonly stripes or solids in the US, and reds or yellows in the UK), pocket all of them, then legally pocket the 8 ball, while denying one's opponent opportunities to do the same with their suit, and without sinking the 8 ball early by accident. In the United Kingdom the game is commonly played in pubs, and it is competitively played in leagues on both sides of the Atlantic.
The most prestigious tournaments including the World Open are sponsored and sanctioned by the International Pool Tour. Rules vary widely from place to place (and between continents to such an extent that British-style eight-ball pool/blackball is properly regarded as a separate game in its own right). Pool halls in North America are increasingly settling upon the World Pool-Billiard Association International Standardized Rules. But tavern eight-ball (also known as "bar pool"), typically played on smaller, coin-operated tables and in a "winner keeps the table" manner, can differ significantly even between two venues in the same city. The growth of local, regional and national amateur leagues may alleviate this confusion eventually.