YaST was created by SUSE to help users manage software and control many SUSE features like the firewall, YOU
, and Samba. YaST stands for "Yet Another Setup Tool".
To open YaST, click on the "KMenu" (the SUSE equivalent of Windows' Start menu), go to "System -> Configuration -> Control Center (YaST)". If you're not logged in as root, you should get a pop up box that asks you for your root password.
There is a lot of overlap between YaST, the KDE Control Center, and the Configure Desktop tool.
An explanation of YaST's Software modules.