In my mind, when the router takes you to another subnet, it is a gateway. And when the router converts ethernet frames to whatever layer 2 protocol frames for another medium other than ethernet, it is a protocol converter.
Understanding the differences between gateways and routers | TechRepublic
Today on a quiz for router benefits I was asked to list a bunch put that (protocol converter) and got it wrong. That guy above argues that it's only considered a gateway/protocol converter when it converts tcp/ip stack entirely.
If anyone can clear it up for certain.