Why do certain commands not show up when you type "help" in cmd.exe?

"netstat.exe is a separate executable that lives in C:\Windows\system32 (or at least it does on XP), rather than being a command within cmd.exe.

There will be a large number of other executables in this folder (and others in the Windows tree) that won't show up when you type help from within cmd.exe."

"I assume most (if not all) of the commands listed under cmd.exe's help are basic/internal commands which are built-in cmd.exe directly.

For instance, try and look for a file named del.exe or del.com, or even a dir.exe or dir.com -- chances are that you won't find it (try: dir /s LookForThisFile.ext). I bet 10$ that most if not all the commands listed under help are 'internal' to cmd and not a binary by itself.

This way of doing things is also used with bash, where help is used to get help on pretty much any keyword provided by the bash scripting language."