Could someone please explain vignetting and barrel distortion?

[cali]

I've heard each mentioned when people talk about lenses but I haven't a clue what each means. Can someone explain in simplest terms what these terms mean?

[Tsmith]

http://www.vanwalree.com/optics/vignetting.html

http://www.vanwalree.com/optics/distortion.html

[Dave_G]

vignetting is when your images have the corners darkened

barrel distortion is when when straight lines are made to look bowed

very simple!

[JCR]

I thought the first one you put on chips with salt and the second is what happens after too many beers.

Ok... i'm sorry I will leave the jokes to the pro's :)