Not all entities should be visible to everyone. 'Set private' enables you to hide certain entities from other users.
In case there is an entity that should only be seen by a limited group of users, mark this entity as 'Private' to hide them from other users.
By default, all users will be able to access an entity. Once the entity has been marked as 'Private', the access of the users will be limited to the basic information of the entity, unless they have been given specific permission.
These permissions can be granted on 'viewers' and on 'editors' level. You have the option to grant access to a specific user or user group.