Commands are expressed using script, a special shorthand language computers can understand with no trouble. Script is an extremely simple language; oddly enough, this is what makes it look so complicated! Whereas normal languages use a variety of embellishments, the form of a script command is always:
The verb expresses what you want your computer to do. There are a fixed number of verbs, although this number is usually quite large. On the author's computer, it reaches almost 1400 in number. But of course, only a handful of these are really necessary.
Sometimes, the verb is all that's written. A verb is always a single word, usually related to the task it performs. reboot is a good example. Entering that on GNU/Linux will reboot the computer—assuming you have sufficient privileges.
Other verbs require more information. These are usually very capable verbs, and must be told specifically what to do. The extra information is given in the form of arguments. For example, the echo verb prints back whatever arguments you type. It requires these arguments to know what to echo. A proper use of echo looks like this:
echo This is an example of using echo!
This script command causes the computer to echo back: “This is an example of using echo!”
Although command verbs are always simple words, like reboot or echo, arguments may have a wide variety of forms. There are textual arguments, numerical arguments—even Lisp arguments. Distinguishing these different types of arguments requires special typing, for the computer to know exactly what you mean.