Once you register for Aadhaar Card, they provide you with a 28 digit Temporary Identifier called EID (enrollment ID). This EID constitues of a 14 digit enrollment no in this format (xxxx/xxxxx/xxxxx) and a timestamp in this format (dd/mm/yyyy hh:mm:ss)
For comprehensive detail on the Aadhaar Card issuing authority and their specific rules/criteria to register are available on the official site link:
For checking the status of your enrollment of Aadhaar card you need to visit this link to check the status on the official website
You shall receive a message stating in case your Aadhaar card is registered successfully:
“Congratulations! Your Aadhaar has been generated and the Aadhaar letter will be delivered shortly.”
If you dont read this – keep retrying at later dates.
In case of positive response, you can check the status of postal delivery of Aadhaar card letter on this India Post website.