what is the difference between bank rate and repo rate?

Repo or Repurchase rate is the rate at which banks borrow
funds from the RBI to meet the gap between the demand they
are facing for money (loans) and how much they have on hand
to lend.

If the RBI wants to make it more expensive for the banks to
borrow money, it increases the repo rate; similarly, if it
wants to make it cheaper for banks to borrow money, it
reduces the repo rate.

Bank Rate

This is the rate at which RBI lends money to other banks (or
financial institutions)

The bank rate signals the central bank's long-term outlook
on interest rates. If the bank rate moves up, long-term
interest rates also tend to move up, and vice-versa.