Along with the usual minor improvements and bug fixes, WordPress 5.0 introduced a new page editor: Gutenberg, a new Theme Template: Twenty Sixteen and a new Plugin: Classic Editor.
The new Gutenberg editor is a major upgrade of the default WordPress page editor. Gutenberg is a “block-based” editor and a first step towards an improved page editing experience.
Blocks provide more
flexibility with how content is displayed, whether you are building your first site, revamping your blog, or write code for a living.
For more information about the new Gutenberg Editor see:
Twenty Nineteen Theme
Twenty Nineteen was designed for the new Gutenberg block editor.
Twenty Nineteen features custom styles for the blocks available by default in 5.0. It makes extensive use of editor styles throughout the theme. What you create in your content editor is what you see on the front of your site.
Visit this link for more information about the new WordPress Twenty Nineteen Theme:
Classic Editor Plugin
WordPress 5.0 Release Notes
Read more about WordPress 5.0 –