Well, if you need diagrams as well, you can look here:
http://auto.howstuffworks.com/torque-converter2.htm


They are definitely worth buying, and even a 2100 rpm stall will make a noticable difference. Just make sure you match it to your engine, and don't forget your diff gears out back as well. It all has to function as a matched package.... Or, you can just get a manual transmission car and dump the clutch at your peak torque .

A word of advice, buy a good quality converter and add a cooler, or you will be spending more money soon.