Aaadhar card is UIDAI (Unique Identification Authority of India) established Jan 2009, under the Planning Commission of India.
Aadhaar Number is a 12 digit individual number issued by UIDAI on behalf of Gov. of India.
Aaadhar card can be used as Identification or residential proof anywhere in India.
How to Download eAadhaar Card
Follow the procedure listed at http://eaadhaar.net/aadhar-card-download/