Friction is a force that resists the movement of one surface over another. It can be desirable but often is not.
It's caused by surface rough spots that lock together. These spots can be microscopically small, which is why even surfaces that seem to be smooth can experience friction. Friction can be reduced but never eliminated
Friction is always measured for pairs of surfaces, using what is called a coefficient of friction.
A low coefficient of friction for a pair of surfaces means they can move easily over each other. Ice and metal have a low coefficient of friction, so metal ice skates slide easily on ice.
A high coefficient of friction for a pair of surfaces means they cannot move easily over each other. Rubber tires and dry road surfaces have a high coefficient of friction, so they tend to grip each other. That means tires don't slide easily when you apply the brakes or turn your vehicle into a corner.
