Model United Nations (MUN) is a copy of the United Nations in content and form. MUN is organized around the world, and students attend from various schools to discuss real-world issues on their committees. Participants represent their assigned countries as delegates on a committee of the conference. The role of delegates is to act as the representative of their delegation to the United Nations. It is to try to solve the problems by taking an active role in the discussions by researching the issues in the committee of delegates, discussing them, writing solution proposals/protocols and presenting amendments to other solution proposals.
And this is a video which explains MUN more detailed: