The term "autonomous body " denotes a self governing body, independent, or subject to its own laws. If autonomous body or institution is a company, it is regulated by the company law. If it is a society, it is governed by the law on registration of societies. But in both the cases, its own board of directors can specify the rules of business for the body/institution. For simplicity sake, normally the boards of such bodies or institutions adopt the rules of the concerned Government or department under which they work, but only by passing of a resolution to that effect.
A society is one form of NGO. In India, one can register an NGO in three different ways - as a society, a trust and a non-profit company (under section 8, Companies Act).
An NGOa non-profit organization that operates independently of any government, typically one whose purpose is to address a social or political issue.