The company handbook, sometimes known as employee manual, or staff manual, is a source for both new and established employees to refer to codes of practice, policies and procedures, company rules and employment legislation.
Whilst it is not a legal requirement, many companies see it is an invaluable business tool in communicating effectively with employees and reducing the potential for ambiguity and misunderstandings between employer and employees.
Staff Handbook content depends on the needs of the business. Often the content is developed by an HR specialist or HR Consultancy like Peninsula or NFU Mutual and increasingly the banks.
Example Handbook contents can be seen here.