There are exceptions though, all coil springs have a slight progressive nature and can be wound to become very progressive by using coils wound tighter in one section or tapered wire. The connecting linkage can be falling rate, straight rate, rising rate or a combination of the three. Falling rate means the suspension rate starts out hard then gets softer. This is a bad thing and the inclusion in a design seems to defy logic. The result is a rough ride over small bumps and the suspension bottoming out over big hits.
Straight rate is neutral and works well for most riding.
The suspension has the same feel throughout the stroke. Rising rate means the system gets firmer as it progresses through the travel. This means a system can work well over little bumps and still have a reserve capable of taking out bigger hits. The key to rising rate is moderation. Too much is a bad thing, doesn't use the middle of the stroke enough and feels harsh, like it has less travel.