What does a gateway do?
I'm a newbie and have noticed many example sketches send data to a gateway.
Is there a gateway overview document (wiki) available on this site?
To put it pretty simply, a gateway is a way to convert and move data from one protocol to another. For example, At some point I am hoping to create a MySensors gateway that will let the MySensors protocol talk to my RCS serial thermostat that runs on an RS485 serial network and uses a protocol written by RCS.