Windows 2003 Server – Sharing folder

Just want to check, my company have win 2003 server and every user in our company have backup folder in win 2003 server and map into their pc.

The question is,why when I want to connect the folder with user pc, I have to use ip address (\\192.168.0.0\user)to map the folder. Before this I just type \\servername\user to map the folder.