A bookkeeper is someone who records the financial transactions for your business. They help put financial information into a standard way to enable your accountants to more easily meet your tax obligations.
Running a business can be very busy, often managing accounts is not your key skill. By hiring a bookkeeper they can manage this process enable you to have more time to focus on building your business.
Costs will vary, often bookkeepers will be paid on an hourly basis to attend your business. Call a few bookkeepers you are interested in and ask them about their fees.
Some bookkeepers may be specialised in one particular software, unless you're willing to migrate your accounting system you need from one who is happy to use your particular software.
A bookkeeper is more focused on day-to-day transactions whereas an accountant's more focused on higher level monthly, quarterly and yearly base accounts.
By keeping accurate records it will enable you to understand your business. By having accurate records it will help you meet your tax obligations as well. If, in the future you decide to sell the business having accurate records will help someone decide whether or not to purchase your business.