A more thorough explanation:

A cash book is a record of all the cash transactions made by a business. It includes all the money received and paid out by the business.

For example, if a business receives cash from a customer, it will be recorded in the cash book as a cash receipt. Similarly, if the business pays cash to a supplier, it will be recorded in the cash book as a cash payment.

The cash book is important because it helps the business keep track of its cash flow. By recording all the cash transactions, the business can see how much money it has coming in and going out. This information is useful for making financial decisions and planning for the future.