4 Channels helicopters are a big step up from the 3 channels helicopters and are basically are not toys anymore but rather hobby products.
They use a professional 4 channel transmitter and 2 micro servos that change the angle of attack of the main rotor blades and by doing that can make the helicopter move in 4 directions: Up/Down, Left/Right, Forward/Backwards and roll to the left or right.
These are products are not recommended to little kids but rather teenagers and adults that always dreamed to fly a helicopter.
Although these helicopters are more sophisticated, they are also quite easy to learn and after a day or two, you'll feel like a real professional pilot.