Friction happens when things rub against one another.
Rub your hands together. Does it feel warm? This is because of friction.
Your hand may look smooth to you, but zoom in very very close, you will see that it is actually rough. The rough edges of one hand catch the rough edges of another, but each hand tries to ‘get away’ and continue to slide. This is friction.
Friction is a good thing to have though. Cars stop moving because of friction between the brake and the tyre.
Let’s try something out. Take your toy car. Give it a push and see how far it goes on a smooth floor. Try the same on a carpet, and on your driveway. Where does the car move the most?