There are 3 types of differences between cash book and pass book namely Timing. Transactions & Errors.

Bank Reconciliation is the process of reconciling cash column of the cash book and bank column of the cash book

Adjusting the cash book for any errors and/or omissions before preparing bank reconciliation is optional when the reconciliation is done at the end of the financial year.

Bank charges debited by the bank is an example of timing difference for the purposes of bank reconciliation.

Debit balance in cash book is same as overdraft as per pass book.