Torque is a popular term when talking about automobiles. So let's start from there.

To get the car wheel spin about the axis, you will need to apply a torque. The force that generates the forque must satisfy these two conditions below:

1) The force must have a component that is tangent to the wheel, in the plane of rotation and parallel to the edge of the wheel;

2) This force has to be applied some distance away from the axis, and this distance is called "lever arm".

 

So torque is actually the tangential force being applied times the perpendicular distance from the axis of the rotation.

Torque is important. For example, if you apply a force that does not have any component tangent to the wheel (such as pushing it towards the center of the wheel or something like that), the wheel is not going to spin, which means you are not applying any torque.

Also, believe it or not, it will be eaiser for you to spin the wheel if you apply your force from the farthest distance possible from the axis. Why? Do you have experience that it's a lot easier to open a door if you push it on the side farthest from the hinges? If you don't know, well, try to push it on the side near the hinges and see how it feels. So, a greater tangential force and a greater perpendicular distance makes a greater torque.