A domicile means a legal claim over the residential status of a particular region. A certificate that helps you prove it is called a domicile certificate.And in turn this helps you in getting home state quota for academic pursuits.  The eligibility criteria for applying for a domicile certificate vary from State to State. We understand that you belong to Maharashtra and hence this answer is being written in that perspective. In Maharashtra, it can be issued only by District Magistrate/Metropolitan Magistrate/ Additional District Magistrate or Competent Authority. There are 5 types of Maharashtra State Candidature. They are Type a,b,c,d,e and you can read them all at: http://view.mahacet.org/mahacet/admin/news_document/Eligibility-Criteria-for-Maharashtra-State-Candidature-Type-Verification.pdf. Then there is also eligibility criteria for Out Side Maharashtra State Candidature and also Jammu and Kashmir Migrant Candidature.