An Olympic soccer team has 11 players on the field: one goalkeeper and 10 outfield players. The same standard applies to association football matches worldwide, whether the competition is domestic, international, or Olympic.
The 11-player structure grew out of nineteenth-century football rules in Britain and was formalized by the Football Association after its formation in 1863. Teams commonly use formations such as 4-3-3 or 4-4-2, but the formation changes how players are arranged rather than changing the total number on the field.
The phrase “Olympic team” can cause confusion because a delegation’s tournament roster is larger than 11 and includes substitutes. The question’s answer refers to the players participating at one time, not the full squad. Olympic football has also had special eligibility rules at different times; in the men’s tournament, most players have generally been under 23, with limited exceptions for older players.