How was the united nations formed and what was its purpose?

The United Nations was formed after World War II, after a mutual agreement that peace and order needed to be maintained between all countries. It's purpose is exactly that— to maintain international security and peace as much as possible.

Hello Snakelover3006112202,

The United Nations is an international organization founded in 1945 after the Second World War by 51 countries committed to maintaining international peace and security, developing friendly connections among nations and promoting social progress, better living standards and human rights. 

Cheers!
-Blizzard