The UN is made up of different agencies - or departments - which deal with all sorts of things, such as peacekeeping, helping the poor, looking after refugees and the environment, ensuring workers' and childrens' rights etc.

The agencies include:

• The UN Environment Programme (UNEP)
• UN Development Programme (UNDP)
• UN Conference on Trade and Development
• UN programme on HIV/AIDS
• UN Children's Fund (UNICEF)
• Office of the UN Commissioner for Refugees (UNHCR)
• World Health Organisation (WHO)

Real power rests with the Security Council, a smaller group of countries that is mainly responsible for peace and security.

There are fifteen council members. Five of them are permanent - the United States, the UK, France, the Russian Federation and China. The other ten are elected by the General Assembly for terms of two years.

The five permanent members have the right to veto. This means they can say no to anything even if the other countries have agreed to it.