reason for libexec?

[Daniel Barowy]

Hello everyone,

  This is, I'm sure, a naive question, so bear with me.  What is the 
purpose of /usr/libexec?  I see from hier(7) that it has something to do 
with "System daemons and utilities (executed by other programs)" which 
probably means, "stuff not normally executed by users".  But it's unclear 
to me how this is different, from, say, /sbin.

  I'm running into this because I've been looking at the spamd code for a 
class project, but I'm not finding a lot of information about libexec in 
general-- there isn't even a mention of it in my big red BSD book.  And 
most of the hits on Google are bits of a long, angry thread about 
libexec's nonexistence in the Linux FHS.

  I don't need a long-winded response.  A prod in the right direction 
would be fine.

Many thanks,
Dan