On Ice Cream Sandwich, an option in the Developer Options is “Show CPU Usage”, which adds an overlay on the screen (see screenshot below).
My question is, how do I read the data ? I guessed that the package names are the process currently actives, but what does the red and green bars behind mean ?
Also what are the 3 numbers on top of the packages ?

This should be the Unix load average. Wikipedia has a nice article about this.
The numbers show the average load of the CPU in different time intervals. From left to right: last minute/last five minutes/last fifteen minutes