Yes, the classic editor is what you are using now. So the plugin will bring that back but I understand this will eventually go away and not be an option. Also, without a plugin, you can choose pages and posts from the dashboard menu and opt to edit them in the classic editor with no plugin installed (also likely to someday be removed), and inside the Gutenberg editor itself there is an option to create a classic block which works much the same, almost identical.
This gives people lots of time and options to adapt to Gutenberg but it’s pretty much certain that at some time Gutenberg will be the only option which I hope will be bug-free and a large improvement overall.
Thanks for the answer. How much is this new editor likely to affect me. I only use basic html such as paragraphs, lists, headings, hyperlinks, and images in posts.
I usually use notepad to write a post or page then paste in to the WordPress editor, will that still be possible?
I also quite often edit already published posts, so is there a chance those posts will be re-formatted when I try to edit?
I haven’t gone into transitioning to Gutenberg too much, as I’ve only played with it on a test site, but from what I’ve seen it converts “classic” posts into the new ones by adding a “classic editor” block to the new gutenberg-enabled post.
It looks like the team is very committed to ensuring as smooth of a transition as possible overall, and there should be support for copy/paste not only from plain text, but also from things like Microsoft Word, Google Docs, and the web. I have not tested that out yet at the moment.