Differ from content_permissions?

When you use the 'content_permissions' module, you can define if a role is able to see or edit the field.

With this privacy module, you can define if an author of a node is able to set a field to private. So other users, even if they have the same role of the author, won't be able to see this field when the author has marked it as private.

You can, roughly, see it as: content_permissions is role based, privacy is user based.