What (rather than who) is Gutenberg?
Gutenberg is the new WordPress content editor, also called 'Block Editor'. Created so you can create richer and more dynamic visual layouts. If you've ever wanted a more 'magazine' style layout this is the way to go. However it does require some learning to get to a point where you'll feel comfortable with how everything works.
You can try it out here… wordpress.org/gutenberg
If you don't want to use Gutenberg for the time being or prefer the original editor there's a 'Classic Editor' plugin. (This is installed and set as default on all the websites we host.)
How to learn to use Gutenberg?
Try it on your own website. You can toggle between 'Classic editor' and 'Block Editor' in the 'Editor' panel on the sidebar of a new page or post. Save a post as draft or private to see how you're getting on.
If you can't see the 'Editor' panel then navigate to Settings > Writing and change 'Allow users to switch editors' to Yes, and save.
Be careful changing between the 'Classic Editor' and 'Block Editor' on existing posts and pages. To begin with you may not end up with what you want so (much) better to practice first.
Try it on the WordPress site wordpress.org/gutenberg