hello rick and welcome to the p2p forum.....
there is one meaning of "gateway" i can tell you about...
usually in reference to the one computer on a LAN with the modem connected to the internet, the other computers on the LAN connect to that via a NIC (network interface card)
common IP address for the gateway computer on a Local Area Network
is usualy 192.168.0.1
most of the other computers on that LAN will be in the 192.168.0.0 range
(192.168.0.2 -> 192.168.0.255)
unless they are on a subnetwork...
if someone is refering to their gateway
more than likley thay are refering to the computer they are connected to ,to get to the internet....
there is a reference in CGI - Common Gateway Interface
dont know if you would mean that one
but you can read about that here
http://hoohoo.ncsa.uiuc.edu/cgi/overview.html
that is more to do with web pages...