See it all the time, but not totally sure what it means?
Employees are all the customer org’s employees. Employees can be assigned to services and will have time sheets connected to their accounts to populate the hours they are working towards an assignment.
Users are the individuals that have some capacity of access to Parallax. Users are the individuals actually utilizing Parallax. The level of access for a User is manage under Permissions.
Typically all Users will also be Employees...
.....but not all Employees will be Users.