crawler.html/crawlers.html? // How to use them?

Question about use of "crawler" pages

[WP1]

Hello,

Where can I get some info on "crawler.html" and/or "crawlers.html".

1. What exactly are they??
2. Is it cool to use them?? (that is, do you get penalized by Search Engines for using them?)
3. Can it be used with "robots.txt" and "<META> tags??

Any and all information appreciated.

WP