Webmin consists of a simple web server, and a number of CGI programs which directly update system files like /etc/inetd.conf and /etc/passwd.  It has been designed to allow system administrators to easily control the server from a user-friendly GUI.  The web server and all CGI programs are written in Perl version 5, and use no non-standard Perl modules.  This means that Webmin will run even if your Apache Webserver has stopped working.

Usermin uses a similar web interface that can allow any user to easily perform tasks like reading mail, setting up SSH or configuring mail forwarding. It can be thought of as a simplified version of Webmin designed for use by normal users rather than system administrators.  Like Webmin, Usermin consists of a simple web server, and a number of CGI programs which directly update user config files like ~/.cshrc and ~/.forward.