What does brake light mean?

["K M" <symbiotic@hotmail.com>]

My dash brake light is starting to cycle off and on.  I don't really 
know what this is indicating but I don't think that it is the emergency 
brake switch.  Any ideas on troubleshooting this "system". Thanks, Kim.   
By the way, this may be the second message that I wrote on this -- the 
first may have been lost in the miasma of the Net.