You can use Google to search for the definition of pixel but it may not help much.
Just take photos of the same object under the same conditions at the different settings. Then examine them on your computer screen using Windows Picture and Fax Viewer. Click on the magnifying glass icon with the + and enlarge the same portion of each photo at least several times.
The difference in the setting should be obvious.
As a former point and shoot person I felt a little overwhelmed at my first introduction to my digital camera (Canon A85). However I feel I now have a good grasp or its capabilities.
EXCEPT PIXELS!
If I take a picture of a scene at 680x480 and then take the same scene at 2272x1704 what differences can I expect?
Under what circumstances would I use a "lower" setting as opposed to a "higher" setting?
I have read a few comments on this subject and most were conflicting and all way over my head. This leads me to my last question.
Is there a source of information on this subject presented in such a way a dummy like me can understand it?
DC

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic