The rebound is how fast the dampers will dampen or resist when your suspension is dropping. In real life situations, if you where to have weak rebound damping, you'd bounce back up if you where to fly over a hump on the road. If you have adjustible shocks i.e AGX KYB and made the rebound stiffer, it'll reduce bouncing back up.
The dampers are the only thing resisting the spring movment. They allow quicker feedback and vehicle responses. They help keep your car from bouncing after you hit a bump.
I have my rebounds set to maximum front and rear to reduce lift at the front while accelerating out of a turn and rear end lift when braking.
The initial LSD setting is how much effect it has when you're not acceleating nor decelerating. Such as when switch back and forth from acceleration when you're in a turn i.e. that point where it switches from while you're on the gas and off of it. I have my rears set at 25 for stability and faster response time because with it at this setting, it's already in effect and it smooths out the LSD transition from initial to acceleration/deceleration. Settings are differnt with different drivetrains.
To me I'd want to set the front as a 1-way and rears like a 1.5-way. I'd put 1-way(I/A/D: 13/25/5 or lowest) to the front and 1.5-way(I/A/D: 25/45/25) to the rear of AWD vehicles. NOTE: The front LSD Setting for the AWD is lower because if set to high, it understeers on high speed turns. IF we where to have it high like the rears in real life situation, it may be better but in the game, we cannot turn as far due to it resisting.
Any more question?