A bookkeeper records the financial transactions of your business.
Keeping track of your sales and purchases, reconciling your bank account and predicting your cash flow.
Organising your financial data on a regular basis.
All of these transactions will be recorded in a standard way so that your Accountant can easily compile your annual accounts.
If you own your own business I am sure you are passionate about running it and concentrating on the tasks you love doing, but not so interested in recording all the details of every financial transaction.