Yast is a package manager distributed by SUSE Linux.
The filosophy of SUSE is to do as much as possible by the yast tools.
/sbin/yast2 is the interactive tool to install and configure applications. Note however, that reading the package database is notably slow: If you see the message Reading package information..., go get some coffee. Or go out for diner. It can take up to 15 minutes(!). You can improve it with a fast network connection and a close mirror, but still: a long wait.
For example, to enable mod_info for Apache2, you need to run yast2, and go to System > /etc/sysconfig Editor, then Network > WWW > Apache2, and edit the APACHE_MODULES parameter (by adding "info" to the list) as explained on Setting up Apache, PHP, MySQL on SUSE wiki.
y2pmsh (Yast2 package manager shell) is a notably fast command line tool to install software.