If you’ve recently set up Wordpress, you may have the version which includes the new Wordpress editor, Gutenberg, from the ‘Gutenberg Team’ (not Project Gutenberg, which is a group that digitizes reading material). It may have been installed as your default editor, or you may have clicked on a button to try Gutenberg; either way now it’s your default editor, and you don’t like it, so you want to uninstall or disable Gutenberg.