I just noticed that my recent post on how to start and shutdown Explorer got a lot of hits.  I was looking at the referer logs and it seems a lot of people have more questions about Explorer.  I will answer some of them:

Q: What is explorer.exe?
A: Most succinctly Explorer is the shell.  When you start Windows and it is just sitting there at the desktop with the Start menu everything you see, at the highest level, is Explorer.  A lot of the code for shell stuff lives in shell32.dll, but explorer.exe contains some code for things like the Start menu and the tray.

Q: What is the difference between iexplore.exe and explorer.exe?
A: The explorer frame is capable of browsing the file system (My Computer, c:\, etc) as well as the Internet.  iexplore.exe starts Internet Explorer, which is the explorer frame browsing the Internet, with all the correct buttons and other UI elements.  explore.exe starts the shell the first time it is run.  If you run explorer.exe again, by doing something like Start->Run->explorer.exe->OK, it launches a file system view with all the corresponding buttons and widgets. 

Q: How do I start Internet Explorer from a command line?
A: Well, you can call iexplore.exe (it usually lives in “%programfiles%\internet explorer\”) and pass an URL as the parameter, or you can just use the 'start' command:

     d:\> start http://www.microsoft.com
     d:\> “%programfiles%\internet explorer\iexplore.exe” http://www.microsoft.com

    I recommend using start.

By far, however, the largest number of hits were from people just searching google for “explorer.exe”.  My guess is they either wanted to get a copy of explorer.exe or they simply had no clue at all what it was and were seeking a description.  I hope this helps them too.