Dear,

The residence/domicile certificate is to be issued by the concerned authority of State Government/Union Territory to certify that the person bearing the certificate is a domicile/resident of State/Union Territory to whom the certificate being issued. Such certificate is issued  as proof of residence to avail domicile/resident quota in educational  institutions and in the State/Central Government services and also in the case of jobs where preference to local candidates is available as per Government of India instructions issued from time to time. 

And its necessary to have a domicile certificate. I would say that If you don't have , make sure you apply for it.

Hope the helps!