Icons - Open

Acts the same as a double click on an icon.  If the icon is a disk or
drawer, it opens a new lister and displays the directory contents.  If the
icon is a project or tool, it will examine the file to determine if it knows
the specific filetype.  If the file matches a previously
 User-Defined Filetype , for which the appropriate function has been
defined, the function is executed.  If the icon is an iconified lister or
button bank it will be deiconified.

If the file does not match a user-defined filetype, it is tested against the
internal filetype definitions and action is taken accordingly.  If there is
still no match, the  Filetype Finder  or the  SmartRead  command will be
called depending on whether you have the  Filetype Sniffer  option enabled.