So what is this Gutenberg Editor all about? It's quite a big change actually, so if you think like a DIVI, ELEMENTOR, Visual Composer style interface, if you think of that type of visual editor where it's not the old classic style editor of a WYSIWYG.
By default, WordPress will include a visual block editor from version 5 onwards which is the biggest jump that they've ever done. You know 4.8 was a pretty big jump with the widget updates etc 4.9 with the WordPress Customizer. Basically, 5.0 is going to ship by default with Gutenberg so if you're somebody that's a bit old-school that still wants to use the classic editor you will need to install it to override Gutenberg.
Before you go ahead and upgrade to the latest version it is strongly suggested that you check your themes and look at your plugins on your existing websites. If your WordPress website is running version 4.2, version 4.3 etc and you update straight to 5.0 with Gutenberg, be careful because who knows what's going to happen. If you've got the ability to you door back up or even do a demo upgrade just to see what the effects are going to be on your website as major releases like this even say like from 4.8 to 4.9 had the tendency of destroying your website depending on how your theme was built, whom you bought it from or if it was a custom design. Also, some plugins may simply stop working or throw errors, so it's strongly suggested that you do a test update and just to see how your website performs.
If your business relies on your WordPress website and you're getting a lot of traffic or you're running WooCommerce and it's the primary source of business you would want to do it in the middle of the night when there is little impact to your business.
Don't just go clicking buttons hoping to see what happens without a backup plan.