What are Sharing Rules?

Sharing rules define access rules for viewing and editing CRM records for different levels of users in the organization. 

Basic rules:

• Admin users have full access to all records. However, read-only fields can only be modified by the system.
• Record owners and superiors have full access as long as their profile permits them.
• Profiles override the privileges granted by Sharing Rules at the user level. For example, if Profiles do not provide Edit permission, then you cannot allow Write permission in Sharing Rules.