Probably the most often used command in Linux is the "ls" command. It is used to list the contents of a directory. For example, if your current directory were "cats" and you wanted to see what it contained, you would type "ls". The output would be the following: lions tigers Unlike many other operating systems, Linux is case-sensitive. In other words, if you type "LS" instead of "ls", Linux will not recognize the command. This applies to filenames, like "lions" and "tigers", as well. Click the right arrow.