Helicopters are usually defined by the number of channels and the size. In general the less the number of channels and the smaller the helicopter the cheaper it will be. The mini / micro helicopters are palm sized making them ideal for indoor fun although they can still be used outdoors in calm conditions. The co-axial helicopters have twin counter rotating blades making them much easier to fly than the single blade ones so are perfect for younger pilots and beginners. The 4Ch single blade are a great introduction to proper helicopter flying and although more difficult to fly are more rewarding when you finally master it. Finally there are the 6ch. The controls on a 6ch helicopter are the same as a 4ch, the extra two channels are adjusted automatically by the helicopter. When you apply throttle the angle of the blades changes to create more lift allowing the helicopter to perform stunts like inverted flight and also fly in more windy conditions.