config.guess is a shell script which attempts to deduce the host type from which it is called, using system commands like uname if they are available. config.guess is remarkably adept at deciphering the proper configuration for your host; if you are building a tree to run on the same host on which you’re building it, we recommend not specifying the host name.
config.guess is called by configure; you need never run it by hand, unless you’re curious about the output.