: An employee is user who can and has an associated to it. He is also present as the Contact in Application. So, we can say that .
: In application like , you can provide anybody with ability to register and use application with that is a User in . A user can also be a contact but a .
Contact is a person who has when it comes to application. A contact is not a part of organization but is usually associated with as a touch point to reach customer. This is a basic detail of all three.
Main point of differences that I can think about these is:
A Contact has and he to application where as a user and employee can login and use .
The Screen to access Contact records is Employee and User share the same screen that but they have different view.
Base table for Contacts is whereas User and Employee are based in . In previous version of Siebel there was table called which was used but in that table in inactive.