Electric powered remote control helicopters have a rechargeable battery to power the engine. All radio control helicopters, electric or otherwise, have a radio transmitter which the pilot (that's you!) operates.
Evidently, the more channels a helicopter has, the more it can do. On a simple 3 channel RC one channel controls the throttle i.e. engine power) whilst the other two operate "servos" - mechanical components that move to change the stability of the helicopter so it can change direction.
Any RC helicopter with cyclic control has a swashplate, and this in turn controls movement of the fly bar (that funny little thing sticking out at right angles to the rotor blade) These servos are called the "cyclics" and both work from one control. One allows forward and back movement of the helicopter (cyclic pitch) and the other allows side-to-side (cyclic roll) Another servo on the tail acts as a rudder, allowing the helicopter to turn as well as remain level in the air.
When a rotor turns, the body of the helicopter wants to rotate the other way - this is called torque. To stop this happening, radio control helicopters must have two rotors counter-rotating to each other. This type of heli is called a coaxial. There is no tail rotor, although there is always a rudder of some kind.
Some coaxial helicopters do actually have a tail rotor, although they don't really need it. Single rotor helis are fixed pitch or collective pitch. Collective pitch RC helicopters have an extra servo on the swash plate (the "collective") that works to adjust the rotor itself. Fixed-pitch radio control helicopters do not have this collective servo, and so the rotor cannot be adjusted. They are easier to learn on, as there is one less channel to operate. Helicopters with a tail rotor usually have a gyro.
