I assume that you are talking about the organization that used to be called the British Commonwealth. If that is what you mean, this is an organization that is made up of 54 countries. All but two of these countries used to be part of the British Empire. In other words, this is pretty much an organization of countries that used to be colonies of Great Britain.
In a lot of ways, there does not seem to be a whole lot of point to the Commonwealth. It is not a political organization like the UN. It is not a free trade zone like the EU. Instead, it is just a sort of club for these countries that works to try to create and maintain cultural ties between them.
The link is to the organization's official site.
The Commonwealth, called the British Commonwelath earlier is a group of 54 nations that were under the rule of the British before they gained their independence. The aim of the group is to co-operate to promote democracy, human rights, and ensure good governance which is in many cases lacking after the British left. As the British ruled over a large number of countries with diverse socio cultural environments, the Commonwealth too has a diverse mix. Also, with India being part the number of people whose governments are part of this inter governmental organization is over 1.5 billion.
Commonwealth, or Commonwealth of Nations is an international organization with the membership of about 54 countries that has been formed to foster cooperation between them in the various fields including economic and cultural. Initially this association was as an organization that were formerly colonies of UK and the organization was called British Commonwealth. Even today the ceremonial head of this organisation is the Queen Elizabeth II of UK. The membership of Commonwealth includes UK also.
The origin of Commonwealth dates back to early twentieth century when, Britain introduced this idea to perhaps keep the people of its colonies happy by giving them some semblance of freedom without really loosening is control over them.
Current activitiwes of the common wealth include promotion of democracy and development, support to youth programs, education, and promoting cultural interchange. A sports competition covering multiple sports is held every four years.