About … exactly what?
The mwLinks website is all about rural areas of Surrey which can be enjoyed free other than, in some cases, parking charges. It especially concentrates on north and central Surrey, although not exclusively. Locations within London boroughs, bordering northern Surrey, are mostly excluded. Therefore, by 'Surrey' is meant the area shown on this map:
The off-road countryside which features on this site includes common land as well as land owned by particular people or organisations. The term 'open access land' has a particular legal meaning and some rather dry comments, rules and regulations are provided by local government and national government but hopefully, you won't need to study this stuff.