Before we explore the commands used to manipulate the Linux environment, we should take a quick look at the structure of the environment itself. Microsoft Windows users will find the Linux file system to be a familiar structure because it is basically the same. You can think of a Linux file system as an upside-down tree. See the diagram to the right. Okay, so it doesn't look a lot like a tree, but try to keep an open mind. In this diagram, dogs and cats are directories. Dogs contains three files, while cats contains two files. Click the right arrow.