Hi,
There are two different processes:

Rechecking
Reevaluation

In rechecking the evalutor checks whether all questions are evaluated and if there is a calculation mistake in the total. Your marks may or may not be increased.

In revealution, your answer sheet will be evaluated again by a different teacher. In this marks allotted for the first time will be nullified and you will have  to accept the new marks.

You can apply for both on the official website of CBSE and the date for the process will be announced soon.

All the best