A helicopter radio provides a separate channel for each of the five functions described below. It has special throttle-collective pitch mixing functions that are not available on airplane radios. These mixing functions make the helicopter much easier to set up and fly. Special features such as throttle hold and idle up also increase ease of flying and aerobatics. More channels may be used for other purposes - gyro switching, lights, landing gear, etc. 

THROTTLE - Moves the helicopter up and down. Transfers engine power to the spinning rotor blades and increases collective pitch to lift the helicopter. 

COLLECTIVE PITCH - Moves the helicopter up and down. Controlled by the throttle through automatic mixing, the pitch of each of the two main rotor blades is directly proportional and changes together or collectively to create the desired movement of the helicopter. 

TAIL ROTOR PITCH - Turns the helicopter right or left (Yaw). This tells the helicopter which direction to face. In the neutral position, the tail rotor blades have 4 degrees of built-in pitch, which enables the model to counteract the torque of the spinning main rotor blades. 

FORE-AFT CYCLIC - Tilts the helicopter forwards and backwards (Pitch). Changes the pitch of the main rotor blades in cycles, which adjusts the pitch (forward and backward tilt) of the helicopter itself. This enables the helicopter itself to fly forwards or backwards. 

LEFT-RIGHT CYCLIC - Leans the helicopter to the left and right (Roll). Acts similar to the Fore-Aft Cyclic, except in this case the helicopter leans to the right or left in order to fly in either direction. 

A gyro is kind of like an "automatic pilot" for the tail rotor function. Generally, the tail rotor is a touchy, difficult function to control (and the most important while learning). A gyro is a little black box that contains special components and circuitry to help you hold the yaw (left and right turning) position of the helicopter. Don't fly your conventional heli without a gyro. All helicopter pilots today, from beginners to experts, use a gyro.