Each pixel represents one sample and the green grid is spaced 10 minutes apart so the complete graphic represents about an hour's processing when you have the analysis window open sampling evey 10 seconds. You can click on this image to display the processes active at times in the past.
The "Active Processes" listing shows server processes which are not awaiting command or that have other processes blocking on them. If the process is holding locks these can be displayed by clicking on the link under the processes "spid" or if a process is being blocked by another spid the locks can be seen by clicking on the column "blocked".
Each time a process is displayed as active the procedure and line number that is currently executing is added to the "Cummulative totals" section. Over time this gives an idea of the areas of code creating the bulk of the load on the server. Click on the link to view the source code.