Distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features.
Here are examples of my distortion photography:
I like these images because in the first photo the background is warped inwards, and the face is dragged out. However, in the second photo the face is flat and you can see a lot more of the background.
Once again the face is contorted out and in the first photo the background is a lot more visible, with the face being very flat.