Rest Grouping

[Retrospectre]

Hello All. I was going over a lesson for music theory and was introduced to rest grouping and the like. Can anyone explain that to me, please? As well as give me a concrete definition for it? As well as the issue about simple duple, compound duple and the like?

[Big Ears]

I can't explain it myself but this might help - rests are at the bottom of the page:

http://www.dolmetsch.com/musictheory15.htm