Most of the times the term ‘Aadhaar Card’ is used, in reality Aadhaar is not only a card. The main potential or power is in the 12 digit NUMBER, the unique identification number that is know as Aadhaar. The number would be the base (Aadhaar) of many services that we are going to see both from government and private sector.
The Aadhaar is not a document like passport. The card we receive is more of a piece of paper that we can keep to remember our Aadhaar number. The real power is the authentication of a person based on his/her bio-metrics (finger prints and iris scan) which will ensure a unique ID for every person.
Find more about it at: What is Aadhaar