Compared to a folder, the file icon actually does something other than just function as a container. If you double-click a program's icon, you open the program itself. When you open a file, it does two things: launches the program that made the file, and then opens the folder and brings it onto your screen. I'll cover the elements of a directory and document window a bit later in this lesson.
The great thing about the Mac Operating System is that many of the skills you use to handle folder icons work in the very same way as file icons. So, you don't have to learn anything new to work with them. This is one of the wonderful features that makes the system so easy to master.