This will make a text file in your home directory, a long file of messages where in case of troubles with your computer you could look for information.
A good site to help you understand those debug messages is:
http://linuxgazette.net/issue59/nazario.html
My advice: execute the command and give the text file a glance, just so you know what ¨dmesg¨ can do for you. As long as your computer runs O.K. don´t bother with the fineprint, but in case of serious problems go in there head first !

Bruno
PS: there is more interesting things to read on that site.
-- May 23 2003 ( Revised Dec 12 2005 ) --