What is the capacity for Company Restricted User

The help menu states: ........You can create restricted users in the owning company and partner companies. Restricted users cannot be added as application administrators and can only view records assigned to their company in specific apps. Restricted users can be given access to add users, but they can only add, edit, and delete users from their company.

Question 1: Define what Specific Apps you are speaking of and what limits or abilities do they have?

Question 2: Added users have only Gmail Addresses. They cannot log into OPC but yet they are consuming a license. Every time they go to log in, they get an error of wrong username/password. They do however receive all notifications for the schedule activities they are assigned to.