Dear student,
Literally, disinvestment means selling of assets. Disinvestment is a policy adopted by the government of India in 1991.In this policy,government sells shares or dilutes control of weak public sector enterprises (industries in which government is a stakeholder of more than 51% shares) to the private sector.
This is done mainly to improve the performance of PSU's (PUBLIC SECTOR UNDERTAKINGS) by eliminating them as they are not profitable to the government.
Regards