Loyd,
Go to Yahoo and do a phrase search on "loop timing diagram". It will show a few articles which provide examples.
I started using them a few years ago and can't really provide a "good" explaination. What I know was picked up OJT via an integrator that I did some work for.
That said, I use loop timing diagrams during the planning phase for programming robotic automation systems where I have to meet or beat a specific cycle time for the overall station. It is a way for me to incorporate each required step of operation and visualize each, via a spreadsheet, in relation to other steps and the overall process. With it, I am able to see the effects of combining certain steps or seperating them. It also allows me to "see" potential problems with movements and such which prevents the "oh s&*t!" at debug start-up.
I am sure you can find more information via the web and others on this site.