If you dont know what is Yahoo Pipes, read here.
The best way to know more about Yahoo Pipes is to start creating one. When I started to explore Yahoo Pipes, I found it very difficult to learn about its pre-defined module from here.
But then I found that Yahoo pipes provides module help in its editor itself. See for yourself.
If you click on the highlighted arrow, it provides you with a help window like this.
ENJOY Creating your Yahoo Pipes !!!