Editing the content in the backend of the content management system has gone through many iterations in Wordpress history.
Pre Wordpress v5 built in editor was a freely available script that has been used in many similar systems, and gives the user a familiar looking toolbar with functionality and look of Microsoft Word or Google Docs.
With the advent of Wordpress v5, this has all changed and is now more in line with how web sites are built in reality. Using the concept of blocks rather than one big content block.
An example of this would be if a client wished to add a table of data. There was no easy way for this to be done without knowledge of HTML, or by adding another plugin and adding more resource hogging files.
Of course there are still other alternatives to the Gutenberg editor, like Visual Composer and Muffin Builder which allows the client to see a visual representation of what the page will look like.
