Here is a link to another WordPress.com tutorial on HTML editing including a video. It is dated but still shows an overall concept if you are familiar with HTML.
This page shows samples of HTML Elements and what the copy looks like when you publish a Page or Post. Displays headings, lists, tables, blocked text, etc., are shown. It would be to your advantage to learn a little basic HTML as you progress (see below).
Note after a comment from my wife Judy: HTML stands for hyper text markup language. It is the coding to tell your computer how you want your typed text or information to be displayed. Samples are bolded text, italics,
strike through, or centered, flush left, etc. These are the behind the scenes formatting when you type something in a word processor, email or in WordPress and then use the icons to change their appearance from the normal or default settings.
There is a simple, free program from CoffeeCup software that you can download and learn how to write HTML language. It is somewhat beneficial because sometimes WordPress gets a little funky, as all programs do. Understanding some basics about HTML may be of benefit to you when this occurs.
Next you will learn about uploading of media (including photos and embedding videos) or Images and Styles.