Helicopter is an aircraft that flies with the help of a rotor like fan that push the air downwards and in response helicopter goes up. Rotor is big enough to lift the weight of Helicopter. The mechanism of rotor is very simple and I think everyone can understand in a single preview of working. I am just describing some aspects of rotor that enable the helicopter to be flying.

There are two rotors in basic type of helicopter. One is mounted on top (Main Rotor) that enable the helicopter to be up in the air and other one is on the tail (Tail Rotor) that balances the torque produced by Main Rotor as a side effect.
Each rotor has two blades at 180(deg) and can also be rotatable at its own axis that makes lift. See this picture.

If blades are at 0 (deg) then there will be no lift in helicopter and if blades are at max angle then Helicopter goes up fast. You can easily understand by imagining this scenario.

Now, about Tail Rotor, Tail Rotor’s main purpose is to balance the torque produced in the response of Main Rotor’s motion. It is also used to rotate the helicopter along the axis perpendicular to the Earth by decreasing and increasing the angles of its blades. See this picture.

In this picture, you can see that Main Rotor is rotating about its mounted point. Main Rotor’s rotates by the force applied by helicopter in anti-clockwise, because of this force, an opposite force will be generated by Main Rotor to helicopter because of resistance produced due to inertia and air and some other factors. This opposite force tries to rotate the helicopter in opposite direction that’s called torque. This process is so fast that’s why this force produces much torque as soon as the rotor speed increases. So balancing of this force is necessary to make the helicopter stable in a direction otherwise helicopter will also rotates and I think, no one will want to enjoy this adventure. So, Tail Rotor is assembled vertically in tail of helicopter that rotates and cancels out the torque to make the helicopter stable. Imagine this whole process. It is really easy to understand.

Now, our helicopter is up in the air. 🙂

Source: wikipedia.com