Preferred terms are "protocol converter" (connects networks that use different protocols), "router" (connects two broadcast networks at layer 3 (network layer). Another example is a mail gateway, which is a layer 7 (application layer) gateway.
2. <hypertext> An interface between an information source and a web server. Common Gateway Interface is a standard for such interfaces. The information source can be any system that can be accessed by a program running on the web server. A typical example is a relational database.