You said your vows in India, and your certificate proves it there. Overseas, though, an officer who has never seen an Indian marriage certificate has no way to tell whether it is real. That is the gap a Marriage Certificate Apostille fills. It is an official stamp that tells the foreign authority the signature and seal on your document can be trusted. In India, the certificate is first verified by the state department, usually Home or General Administration. The Ministry of External Affairs then adds the apostille. After that, countries that are part of the Hague Apostille Convention generally accept it as it is. If your destination is not a member, the document goes through embassy attestation instead. You will usually be asked for it when applying for a spouse or dependent visa, joining family abroad, opening a joint account, buying property or updating your name on foreign records. Most delays come from small things, like a blurred copy, a spelling that does not match the pass