1. You tell the computer what to do with single words typed into the computer one at a time. Modern computers appear to have done away with the typing of commands by having beautiful graphical displays that work with a mouse, but, fundamentally, all that is happening is that commands are being secretly typed in for you. Using commands is still the only way to have complete power over the computer. You don't really know anything about a computer until you come to grips with the commands it uses. Using a computer will very much involve typing in a word, pressing , and then waiting for the computer screen to spit something back at you. Most commands are typed in to do something useful to a file. From Rute-Users-Guide