Hi Saakshi,

AIIMS online registration is a two stage process.

1. Basic Registration

2. Final Registration

In the past majority of rejections happened due to improper filling of details other than educational qualifications. So in the first stage applicants will be able to register by filling basic details and uploading images almost six months in advance. These particulars and images will be screened and there would be adequate time to correct errors and deficiencies.

The main idea is to avoid last minute rush and fear of rejection of applications. In the below link you can find notice to know more details about the process.

https://www.aiimsexams.org/pdf/Imortant%20Notice%20No.%2081-2018%20PDF%20File.pdf

Hope this helps you.

Good Luck!!