It literally means ‘we command’. It is a command issued by the court to a public official asking him to perform his official duties that he has failed or refused to perform. It can also be issued against any public body, a corporation, an inferior court, a tribunal or government for the same purpose.

The writ of mandamus cannot be issued:

(a) against a private individual or body;

(b) to enforce departmental instruction that does not possess statutory force;

(c) when the duty is discretionary and not mandatory;

(d) to enforce a contractual obligation;

(e) against the president of India or the state governors; and

(f) against the chief justice of a high court acting in judicial capacity.

Source: Indian Polity by Laxmikanth