MadWifi is short for Multiband Atheros Driver for Wireless Fidelity. In other words: it is a Linux kernel device driver for Atheros-based Wireless LAN devices. The driver works such that your WLAN card will appear as a normal network interface in the system. Additionally there is support for the Wireless Extensions API. This allows you to configure most aspects of the device using common wireless tools (ifconfig, iwconfig and friends).