This is the demo post that WordPress provides when you first use the Gutenberg Editor interface.

The goal of this new editor is to make adding rich content to WordPress simple and enjoyable. This whole post is composed of pieces of content—somewhat similar to LEGO bricks—that you can move around and interact with. Move your cursor around and you’ll notice the different blocks light up with outlines and arrows. Press the arrows to reposition blocks quickly, without fearing about losing things in the process of copying and pasting.