Hi Jaanu,
Very simply speaking, as per Company Law, 1956:
A Private Limited Company is one whose equity is held closely (privately) among stakeholders, being not less than 2 and not more than 50. The shares of such a company are not traded publicly. The provisions also specify the constitution and appointment of the Board of Directors.
A Public Limited Company is one whose equity is held publicly. Thus, a Public Limited Company can be promoted by a minimum number of promoters eligible for the purpose (not less than 7). The shares of such a company are registered in a stock exchange and can be traded. Obviously, the issue is governed by the jurisdiction of regulatory authorities functioning under the RBI guidelines.
Hope for the time being this information is good enough.
Bye,
Bibhu Prasad Das :-P