As per the new rules, to book Tatkal tickets, IRCTC account will have to be verified with the Aadhaar number, and for this, a new rule is going to be implemented from July 1. To prevent duplication and other frauds, many government departments, banks and even telecom service provider companies now issue SIM cards through Aadhaar authentication.
The Unique Identification Authority of India (UIDAI), the authority of the Government of India that issues Aadhaar numbers, submits the demographic information (name, date of birth, etc.) or biometrics information (fingerprint) of every person along with their Aadhaar number to CIDR, which is a unit of UIDAI.
This is how the whole process of authentication works:
It has an authentication agency or service provider who initiates the authentication request. The agency processes the data and sends it forward. The Aadhaar number of the person and related data is submitted, in which demographics or biometric data has to be submitted. This request goes to UIDAI's CIDR. The request is verified by CIDR.

After this, UIDAI's CIDR processes the submitted request. After this, the CIDR agency matches the data with the biometrics available to it, and when this work is completed, the authentication process is completed.
There are 2-3 ways of Aadhaar authentication. These include face authentication, fingerprint scanner, and OTP authentication. In the biometric process, users have to scan their finger or face. Authentication can also be done through OTP, in which OTP is sent to the registered number of the Aadhaar cardholders.
Offline authentication can also be completed by scanning the Aadhaar QR code. The Internet etc. is not required for this. For this, one can use the Aadhaar mobile app.
Aadhaar authentication is a process of verification, which takes place both online and offline. Under this process, any eligible agency can initiate the authentication process, after which the UIDAI agency verifies the details and biometric details. When the verification is complete, the request-initiating agency is informed.