A client pays you. A member belongs to you. A staff member is paid by you. Three relationships, three records, side by side.
A church has members, employs staff, and has clients on the day it sells something. WBAMS keeps each level as its own record rather than renaming one into another. Setup › Management Levels switches levels on; clients cannot be switched off.
Call them what you call them
A clinic says Patient, a club says Member, a studio says Artist. Set the singular and plural word each level is shown under; the records behave the same whatever they are called.
One person, one login
The same person can be a client, a member and a staff member with one password, and every record lists the others. A level record needs no login at all: most members never sign in, and plenty of staff never open the billing system.
Nothing is deleted by a switch
Turning a level off hides its screens and keeps every record. Turning it on creates its tables at that moment.
Full guide
The complete reference is Management levels in the WBAMS documentation.