In Linux there is what is called a PATH. It is a list of directories where programs are looked for when you type them in at the command line. For instance the command ls is in /bin. If you do a
you will notice that directory is in your PATH.
Most system config commands are in /sbin and /usr/sbin. These directories are not by default in a users PATH but are in root's.
If you "su -" to root then those commands can be accessed with a ifconfig. But a normal user has to do /sbin/ifconfig
If you want those commands in your PATH then add this to ~/.bashrc
Hope that was clear.