The user interface interprets the command and passes the program name to the file system, which reads the directory.
When a Mac is turned on the Finder program is automatically launched and it provides the desktop.
finder
Finder.
The "Windows Explorer " program is launched.
Windows desktop and The Recovery Console
how do you open a program located on your desktop
Innumerable. Remember that any program on Linux can be launched from the command line, so there are as many commands as there are programs.
The Finder is the program that is automatically launched when a Mac is turned on.
The Etruscans launched a building program that turned it into a city.
If something get "stuck" or display wrong on your desktop as often if a program stops working you can refresh your desktop. It will re-draw everything on your screen removing anything visual that shouldn't be there.
headlines
There is no standard reader for manpages for a graphical environment. You can either use the man command in a terminal emulator, or a graphical program like Tkman or TkViewMan.