A Guide to Sharing Architecture

Sharing model is an essential and critical element of salesforce. It enables record -level access control for all the custom objects and many standard objects. 

License: 

It is essential for every user in salesforce to have a minimum of one user license. 

They are the keys to enable functionality. 

Types of licenses:

·        Full Sharing Model

·        High Volume Customer Portal License

·        Chatter Free License

Components

Profiles and Permission Sets

•  These provide object level security (CRED access to records)
• “View All” and “Modify All” permissions for objects bypass sharing rules and settings. 
• This is also a preferable alternative to “View All Data” and “Modify All Data” administrative permissions.

 Record Ownership and Queues

•  Owner of the record has full access to the record
• Users higher in a hierarchy inherit the same data access as their subordinates for standard objects

 Queues

• Manage your leads, orders, cases, service contracts, and custom objects by using Queues
• Records in the queue can be assigned or owned by the queue members or users above them in the role hierarchy.

 Organization-Wide Defaults

•  Organization-wide defaults are the only way to restrict user access to a record.
• Defines default level of access that users have to the records
• Locks down your data to the most restrictive level
• You can remove the grant access to the managers in the role hierarchy by unchecking Grant Access Using Hierarchies setting for custom objects.

Note: Grant Access Using Hierarchies setting cannot be changed for custom objects.

I strongly recommend to watch : Who sees what video