A distortion is a change, twist, or exaggeration that makes something appear different from the way it really is. You can distort an image, a thought, or even an idea. To say that I never take out the garbage is a distortion of the facts.
The heat from the highway creates a distortion in the way objects in the distance appear: They wiggle and dance. The heat creates a wavy distortion in the air that shakes up the image of the things beyond it. Things are the way they are: to change them is to distort them or to create a distortion. Some guitar players prefer distortion: they plug their instrument into amps and pedals that twist and stretch the sound so much that you might not even recognize its source as a guitar.