Gutenberg is a new block-based content editor that will replace the current editor interface in WordPress 5.0, scheduled for release on November 19th. The new editor structures all content as blocks that have properties and can provide layout structure. Sites may break or have issues with Gutenberg, especially those using page builders. It is recommended to test sites with Gutenberg before the 5.0 release to identify and address any problems. Plugins are available to disable Gutenberg for sites that need more time before transitioning to the new editor.