Gutenberg is the default WordPress page builder. It was introduced in 2018 and replaced what’s now called the “Classic” WordPress editor, which was the original rich text/HTML content editor without any drag-and-drop functionality.
Gutenberg was actually a response to a wave of third-party page builder plugins, including Elementor, Divi, and Visual Composer, which all came out to replace the Classic Editor.
From a feature standpoint, Gutenberg offers an easily accessible “block” library for dragging content elements onto the pages and posts.