From time to time Recap speaks volumes to me. Below I'll try to layout some of the scenarios I've encountered and what they might mean.

Typical Idle

This is typically what many systems look like when they are idling. There are always a few (dozen) background processes running, and this usually results in a little disk activity.

Transition

This is an application transitioning from working on a disk-bound problem into a CPU bound problem.

I'm Givin' Her All She's Got, Captain!

A continuation of the well-behaved CPU bound application above.