The Indian Institutes of Management (IIMs) are a group of 20 public, autonomous institutes of management education and research in India. They primarily offer postgraduate, doctoral and executive education programmes.

Each IIM is autonomous and exercises independent control over its day-to-day operations.

There are approx 18 IIM's. You can check the complete list here.

Each IIM has there own selection criteria, fees structure, college rules and regulations.

You can check the reviews/ratings of each by clicking on the college name given in the above link.

So there is a UG program integrated which is BBA+MBA that is 5 year program and the admission is through IPMAT entrance and then there is 2 years MBA program for which scores of CAT is accepted mainly following with other rounds. Let me know for which course you are asking for?