The tail rotor keeps the helicopter pointed in one direction. Without it, the helicopter would just spin around in circles. Some helicopters can have as many as six main rotor blades, and up to five tail rotor blades. Skycam 16 has two main rotor blades and two tail rotor blades. A powerful engine located either under the main rotors or in the tail is used to turn both sets of rotors.
Helicopters are safe to fly in.
It's true that if the engine stops working the helicopter will start to fall. But a good pilot can use the air rushing by to make the main rotors turn and land the helicopter relatively gently. Helicopters have many different uses The army uses them to move troops and equipment quickly. They even use special helicopters to search for enemies. Many cities have air ambulances.