Description of "files" under /proc

[Richard Owlett <rowlett@cloud85.net>]

In another forum there was a discussion comparing execution times of 
some different programs accomplishing the same task. The programs were 
being run on different machines.

As part of the discussion the use of "grep MHz /proc/cpuinfo" was 
suggested. That prompted me to investigate the /proc directory.

Is there somewhere that catalogs the function of the various "files" 
under that directory? What are the functions of the sub-directories with 
a numeric name?

TIA