Understanding Something?

I am reading in Chevy High Performance (yes that's right CHEVY) and they are talking about how to wire a lockup converter pressure switch and they don't go into much detail at all as to what it is and what that does. Can someone please explain it to me? All it really says here is something about small block chevys with deep rearend gears running the quarter mile at over 7,000 rpm.
Thanks for any help.

If you run a car on the street with a lock-up converter, and you don't lock it up in overdrive, it will overheat. Also, it needs to unlock when you hit the brakes.

Go to this site, enter and click on "Wiring."

http://www.700r4.com/

Alright I see. Thanks. Can anyone else explain it more in detail of like how it works and all? I think I kind of get it like I understand what Henry said but not too great. Sorry if it's a dumb question but like I said, I won't learn unless I ask.

Thanks again.

Well I am a lazy bum so I can't. Isn't that what these forums are for anyways because all these questions I see on here can be answered on the internet too then.... ?

http://www.700r4.com/tech/tcc/index.shtml

Thanks.