The United Nations is an international organization whose aims are to facilitate cooperation in international law, international security, economic development, social progress, human rights, and - perhaps most importantly - achieving world peace.
Like the real UN, MUNA is divided into several committees. The main bodies at MUNA are in some ways different than at the real UN for practical reasons. For example, instead of a Human Rights Council and a GA2 on Economic and Financial affairs, MUNA works with a GA2 on Human Rights.
MUNA also houses the Historical Committee, dealing with important issues that have happened in the past.
More information about the real UN you can find here: United Nations
More information about different global issues discussed by the UN you can find here .
A good website discussing global issues you can find here .
You can find more information about each main body on the right.