In short, a Department manager has similar functionalities to an Admin, with the only exception that it is restricted to his/her department. Following is a listing of the main functionalities/differences:

Admin > Department manager > Staff

Admin
1. Access to ALL departments (all diary questions, all patients, etc.)
2. Access to ALL functionalities in settings (this includes all departments)
3. Can create/edit care paths
4. Can see ALL staff members (this includes other Admins)
5. Can create other staff members (this includes making another Admin)

Department manager
All key points are applicable only at their department and level.
1. Access to their department only (can see patients at their department only, etc.)
2. Access to settings (Excluding: different departments)
3. Access to staff members (Excluding: admins)
4. Can create new Staff or Department manager (NOT an admin)

Staff
1. No access to settings
2. Can't see other Admins in the list of staff members.