Note: WordPress has developed an interactive demo for the Gutenberg editor at here.
Simply speaking, the Gutenberg Editor within WordPress is a visual-based editor that will enable users to build visually stimulating pages and posts without the need for knowledge of HTML, CSS, etc.
According to WordPress-
"Gutenberg looks at the editor as more than a content field, revisiting a layout that has been largely unchanged for almost a decade. This allows us to holistically design a modern editing experience and build a foundation for things to come"
Gutenberg will enable the use of "blocks" which allow you to insert, rearrange, and style multimedia content with very little technical knowledge. Instead of using custom code, you can add a block and focus on your content rather than moonlighting as a Developer.
Okay, okay- but should I use Gutenberg or the Classic Editor?
Ultimately, the choice is personal. For bloggers that are image/video-centric, Gutenberg may be the better choice because of its ability to enhance visual engagement. For bloggers that are less about images, the Gutenberg editor may overcomplicate your workflow.
As of August 2018, all Boarding Area blogs are the Classic Editor installed and activated and you will see no change when WordPress incorporates Gutenberg as the default editor in v5.0.
Even if you aren't a visually centric blog, WordPress is predicting that the Gutenberg Editor will be "just as simple, if not more so" than the current editor.
Here's a fun GIF they made to demo-
But what about any previous customizations? Will they still work?
To the best of our knowledge, yes. WordPress has stated that the Gutenberg Editor will continue to support any previous PHP. Additionally, WordPress has advised that any Custom Post Types previously developed will continue to be available with the new editor.
You can find more in-depth information about the Design Principles surrounding the Gutenberg Editor here.