As per Section 390 of Indian Penal code

Theft is "robbery" if, in order to the committing of the theft, or in committing the theft, or in carving away or attempting to carry away property obtained by the theft, the offender, for that end, voluntarily cause or attempts to cause to any person death or hurt or wrongful restraint, or fear of instant death or of instant hurt, or of instant wrongful restraint.

Extortion is "robbery" if the offender, at the time of committing the extortion, is in the presence of the person put in fear, and commits the extortion by putting that person in fear of instant death, of instant hurt, or of instant wrongful restraint to that person or to some other person, and, by so putting in fear, induces the person so put in fear then and there to deliver up the thing extorted.