The Commonwealth is a family of 54 countries, spread over every continent and ocean in the world. Although the people of the Commonwealth are different in many ways, they work together by sharing ideas and experiences, skills and knowledge.
About 30% of the world's population live in the Commonwealth. That's over 2 billion adults and children.
The Head of the Commonwealth is Her Majesty Queen Elizabeth II.
The Secretary-General of the Commonwealth is Kamalesh Sharma, an Indian diplomat.
Watch this video and find out more about the Commonwealth:
Every 4 years, all the countries come together to celebrate the Commonwealth Games, also known as the "friendly games" because it is the individuals who compete rather than the countries.
The next Commonwealth Games will be held in Glasgow, Scotland, in 2014.
The Commonwealth theme for 2013:
Opportunity through Enterprise