📡 Channel
One controllable function on a radio system — steering is a channel, throttle is a channel, an aux switch is a channel.
A basic 2-channel radio does steering + throttle; planes, helis and drones often use 6+ channels for flaps, gyro gain, flight mode and more.
What it actually does
A channel is one independently controllable function. Steering is one, throttle is another. A basic surface radio has two or three; an aircraft needs at least four; a scale crawler with lights, a winch and a two-speed gearbox can use six or more.
In practice
Channel count is the practical limit on what you can add to a model. The third channel on a surface radio is usually a switch or dial, used for a two-speed, a locking diff, lights or a winch. Aircraft channels map to throttle, ailerons, elevator, rudder and then flaps, gear and flight modes.
Worth knowing
Buy with a channel or two of headroom. Outgrowing a radio because you added lights is a frustrating reason to replace an otherwise good transmitter.