RC-Helicopters generally consist of a rigid body housing the engine and main rotor assembly, as well as a tail boom with a tail rotor. Stability has to be achieved manually, with most helicopters using a Gyroscope (or "Gyro" for short) to stabilize the tail. RC/Helicopters can be powered by a glow engine using a nitro-methane based fuel, gasoline fueled two-stroke engine, rotary turbine, or using an electric motor.
While electric powered helicopters are advantageous due to their quiet power-trains they are limited in duration of flight as compared to a comparable liquid fueled helicopter. However, they are cheaper to run, than a comparable nitro-methane powered unit. Cheapest by far to run are the 'gassers' which run a gasoline-oil mixture not unlike a weed-whacker or a small gas powered scooter.
R/C Helicopters come either as a kit, almost ready to fly (ARF), and ready to fly (RTF). A kit can be challenging to someone new to the hobby as a helicopter has many moving parts and requires extensive assembly and set up. An almost ready to fly model may be a better choice from someone new to the hobby. Work in a well lit area as some of the parts especially on a micro helicopter can be very small (1.5mm nuts are the size of a crumb!). It is also essential to use a thread-lock on the threads of every threaded connection. Be sure to use the blue threadlock, not the red, as the blue formula allows subsequent dissassembly.