Trademark
A registered right to a name, logo or mark for particular goods or services, which stops others using it for the same.
A trademark protects the name customers know you by. Registration is with the Trade Marks Registry (ipindia.gov.in), which also has a public search you can use to check a name before you build a business on it.
Registering a business, a GSTIN or a domain does not give you the trademark. If the name is going to carry real value — on packaging, a franchise, a second city — it is worth a word with a lawyer about protecting it.