rebound damping

[bergspre]

I have asked here before about spring preload and I think I understand what thats for, to make it higher so it doesnt bottom out.

But what is the rebound damping for?

I just read my clymer manual and it said the xt600 has rebound damping adjustment too,at the bottom of the rear shock you can turn it manually by hands on different clicks and 4-5-6 setting means "stiff".

I thought XT only had 1 adjustment on the rear shock/spring preload. But I guess this is good news Though I dont know yet what its for it must be good for something.

Im 123KG now and the rear bottoms out on some bumps also i can feel that it gets much lower when i sit on it..lower rear the front.

Combined adjustment of spring preload and rebound needed? (compared to stock setting+my weight)