Seems you need a lot of basic clarity that cannot be explained completely in a comment.
https://groww.in/p/what-is-esop
Broadly: check the ESOP policy document, share price of the ESOP(as per latest valuation report), number of shares being offered to you, cliff period, vesting schedule.
Vested esops can't be sold in open market typically. Companies buyback those in a specified period from you once you leave the company.
Some companies grant it free of cost, others ask for face value, and some give it with discount when you exercise it.
There are a lot of nitty gritties beyond this, but having a clear ESOP policy will clear most of it. Feed your ESOP policy to some good LLM, you'll understand the rest.