Each letter is assigned a numeric value that will fit in eight digits of binary notation. Text editors can be wonderful programs. The biggest advantage is the price. There is probably already one or more installed on your computer. You can find a number of text editors for free on the Internet.
Text editors are also very easy to learn.
Since they don't do a lot of fancy things, they are generally less intimidating than full fledged word processor packages with all kinds of features. Finally, text editors are pretty universal. This is often not the case when using fancier programs. It is a very good way of storing text information, but it has no way of handling more involved formatting. Text editors generally do not allow you to do things like change font sizes or styles, spell checking, or columns.