This tool configures your system so that it will act as a gateway for other machines connected to it via a LAN. To do so you will need an already configured connection to the Internet as well as a network connection to your LAN. This implies at least two Interfaces, for example, a modem and an Ethernet card.
After you complete this wizard, all computers on the network will be able to access the Internet as well.
Basically, a DHCP server is installed on the machine. Then you simply tell all the clients on the local network to use it by configuring the clients to use automatic IP configuration (DHCP). This way they can auto-configure themselves to use the Mandrake Linux machine as a gateway to the Internet.