Windows 2003 server questions

Hello there,
I’m new to Windows 2003 server(Small Business version). I’m setting a network for 30 employees in one location. I started to set up users under the Server Management utility.

1- My question is do I need also to set them in Active Directory?? I’m guessing in our stiuation(one location and one server) there is no need to use Active Directory??

2- Also, what’s the purpose of client computers?? should the client computer id match the computer’s name??

Please advise.
Canaan.