As a description used for a skype image they probably mean the same thing "not right". Distortions, in general, come in many forms. piece missing, bent, where straight lines become curves, colour changes, noise, colouration, or spots, dots, regions affected by intensity or colour changes, or out of place. Also blur is possible as things are often coded as coarse first, then detail. This means you often get he coarse image first, then sometimes the details never arrives in good condition, so you are left with a blurry, distorted image. Distortions of shape would be unlikely on skype. Colour, or regions, more likely. Choppy, generally would be taken to mean, cut up into pieces, either in time, or area of the image. . Delay in any moving item such as video, or a mouse could create the same effect, if different parts update art different rates or at different times.

It means basically the same thing. When they said that their screen was 'choppy' they meant that the video was lagging and freezing on certain frames, or was very pixelated. Hope this helped!