It's a black art, alright...
So now you have some idea of compression/rebound, etc.
Here's how it's most frequently structured, fork or shock:
Most low-end stuff only has low-speed rebound damping (NOT dampening).
Mid level stuff often has low-speed rebound and compression damping and often lock-out too (so it stops moving all together).
High end stuff now usually has high and low speed rebound and compression damping, and lock-out if applicable (e.g. downhill stuff rarely has lockout) .
Pre-load mainly applies to coil springs (air springs can use a negative spring to the same effect) and simply places some pressure on the spring before you even sit on the bike to make the suspension sit at the right level for your body weight (sag).
All of the above really serves to control how fast the spring moves - how fast it squashes (compression) or returns to unsquashed (rebound).
The spring can be squashed fast or slow (or any speed in between) but we use the terms 'high' and 'low' speed to really differentiate between how the spring moves under the rider's input (body weight/pedalling bobbing - low speed) or impacts from higher speed from the ground (high speed damping).
Hope that also helps a bit...