Friction is the force that tries to stop materials from sliding across each other. There is friction everywhere. There is friction between your hands when you rub them together, and friction between your shoes and the ground we walk on.

Fluid friction
Liquids and gases are called fluids. They can also cause friction. When a car is travelling fast on a motorway, air resistance is by far the greatest frictional force pulling against it. Fluid friction increases with speed, so, for a moving vehicle, more speed means more air resistance.

Advantage of friction

To stop quickly, a car must lose speed rapidly. A high braking force is needed for this it is provided by friction between the tyres and the road.

A car would not move if there was no friction between the tyres and the road.

Disadvantages of friction

- Makes movement difficult
any time you want to move an object, friction can make the job more difficult. Excess friction can make it difficult to slide a box across the floor, ride a bicycle or walk through deep snow. An automobile would not move forward very well unless its friction was not reduced. Oil is needed to lubricate the engine and allow its parts to move easily. Oil and ball bearings are also used in the wheels, so they will turn with little friction. 

Wears things out
Any device that has moving parts can wear out rapidly due to friction. Lubrication is used not only to allow parts to move easier but also to prevent them from wearing out. Some other examples of materials wearing out due to friction include the treads of a tyre.

-Heats parts
The Law of Conservation of Energy states that the amount of energy remains constant. Thus, the energy that is "lost" to friction in trying to move an object is really turned to heat energy. You've seen how people will try to start a fire by vigorously rubbing two sticks together. Or perhaps you've seen an automobile spin its wheels so much that the tires start to smoke. These are examples of...