The default organization-wide sharing settings for Standard Objects are:
|Calendar||Hide Details and Add Events|
|Campaign||Public Full Access|
|Contact||Controlled by Parent|
|Custom Object||Public Read/Write|
|Opportunity||Public Read Only|
|Users||Public Read Only
Private for external
Public Full Access:
This option is available for setting the Campaign object only along with other access options. Through public access the user can have the ability to search records, reports, add related records, edit details of the records and can delete the record.
When the Campaign object is set to public full access, all users in that organization can be able to view, edit, transfer and delete.
This option is available for Leads and Cases objects only along with other access options. When lead or case objects are set to public read/write/transfer, then all users can view,edit, transfer and report on all the case and lead records.
Whenever a record is set to public read/write the user can view, edit and report on all the records.
Public Read Only:
When a record is set to public read-only the user can search the records, view and report on every record but the user cannot edit that record. Only record owners and assigned users can edit that records.
When a record is set to private only that record owner and users above that role in an hierarchy can view, edit and report on those records.