As well as the rules, there is information on road signs and markings, penalty points, vehicle maintenance, etc.
Certain rules in the Highway Code represent various laws and must be obeyed. Other ones are not compulsory, but advisable. The Road Traffic Act 1988 says A failure on the part of a person to observe any provision of The Highway Code shall not of itself render that person to criminal proceedings of any kind, but any such failure may in any proceedings (whether civil or criminal and including proceedings for an offence under the Traffic Acts, the Public Passenger Vehicles Act 1981 or sections 18 to 23 of the Transport Act 1985) be relied upon by any party to the proceedings as tending to establish or negative any liability which is in question in those proceedings.
The Highway Code is published by The Stationery Office, ISBN 0-11-552290-5