Hi Chethan!!! The UPSC exam is divided into three parts:- 1)Prelims 2) Mains 3) Interview. For prelims and mains you should learn the following subjects:

1. History
2. Geography
3. Political Science / Civics
4. Economics
5. General Science - Physics, Chemistry & Biology
6. Environmental Science
7. Sociology

There are some additional optional subjects for mains and for interview there isn't any specific syllabus.For more details you can refer to this link : https://competition.careers360.com/articles/upsc-civil-services-exam-pattern-syllabus



All the Best.

Hope it helped.Thank you.