FYI you can get this same info in the terminal itself. For a list of all commands starting with the same character (or set of characters), at the terminal prompt type the first character(s) and then press tab twice. The shell will try to complete the command on the first tab from all those available, and then list the remaining ones on the second tab. From there you can see the list of commands, and then use the built in "man pages" to look up a specific command.
For instance, if I'm looking for a command "ipconfig", I can type in "i <tab> <tab>" and get a list of all the commands that start with the letter "i". ipconfig is one of those commands, and is listed in the results. I can also narrow down the output list by furthering the initial command to "ip <tab> <tab>", which will give me all available commands that begin with "ip".
From there I can see the "ipconfig" command, and know it's available to me (many commands on some UNIX/Linux distributions are not included in others -- OS X included). From there I can run "man ipconfig" to print out the manual page (man page -- those listed on the site baltwo linked to) and look up the command information.
This puts reference information right at your fingertips, instead of having to open your browser and look up the command there. Additionally, if you are ever in a situation where you do not have a GUI and are only dealing with the command line (such as single-user mode) then knowing how to access a command's man pages in the terminal can be very useful.
Thanks for the feedback. As Mr. Kessler noted, you could do most of that stuff in the Terminal once you learn how. The link I posted lists everything without guessing. Good computing.
