Essentially, it's a digital typewriter (or as close as I can make it).

That means a few things, but the biggest ones are:

• No cursor. The "paper" moves left to right under a caret (the bottom red triangle) in order to place the next character.
• No word wrap. A "ding" warns you when you're reaching the right margin and you with do a carriage return, which moves that paper up one line and back to the left margin.
• No backspace. Hitting backspace or delete will move the carriage back however many spaces, but it doesn't delete what is typed. Instead your new characters are on-top of the old ones, just like a typewriter. If you want to "delete" a word, there's a "correction tape", which allows you to retype over the word in "white ink", effectively erasing it. Or you can simply do what I do on a typewriter, which is go back and cover the error with xxxxx and keep moving forward.
• Related to the above, there is no block selecting of text. For all intents and purposes, what you've typed is immutable. Like typing on a piece of paper, once it's typed, it's typed. The correction tape gives you a limited ability to correct errors, but trying to do that for an entire paragraph would be a pain in the butt.
• (optional) only your last ten pages are visible. As new pages are added, older ones move into a "done" folder so you can't fall into a continuous editing cycle instead of making forward progress.