Like the shell, Adventure‘s interface is made entirely of text.
You interact with the world of the game by typing commands and reading responses. ENTER BUILDING or GET LAMP, for example.
The shell is a lot like that game world, except that instead of a map full of rooms and objects, you navigate a computer’s filesystem and work with the files it contains.
The filesystem, everything the operating system needs to boot up, run software, save files, take photos, etc. is organized into directories. We usually call these “folders” in the Windows and Macintosh worlds, but the concept is the same. A directory is just a special kind of file that can contain other files, including directories.