What are the essential differences between the IMF, World Bank and the UN?

Answer 1

IMF is the lender of last resorts meaning any country has Balance of Payment problem they stand ready to help that country out.
World Bank provides developmental loans to countries that need their loans.
UN is a group of all countries created to delibrate on International trouble as and when it happens anywhere in the world, where it consists of a Security council of five advanced nations and ordinary members which are all other countries.

Answer 2

Wesley! you've got it all from Mathew I cant add to that!!