Issued by the Unique Identification Authority of India (UIDAI), the Aadhaar card is one of the most important of all documents that serve as proof of identity for an Indian citizen/resident. The Aadhaar contains a unique 12-digit number for identification along with the photograph, personal details, biometric information, and the demographic details of the Aadhaar holder. This means your Aadhaar must be free from errors and the information stored needs to be updated whenever there is a requirement.