With WordPress 5.9 on track to be released on the 29th January 2022, it will bring with it Full Site Editing (FSE). In order to be able to use the full site editing feature in WordPress, you will need to be using a block-based theme.
If you want to watch a preview of new features coming to WordPress then you should watch the State of the Word for 2022 from the 14th of December.
Full Site Editing
Full site editing will allow you to directly edit all parts of the site from templates to how the site looks. It will come with a number of site blocks which make it easier when the feature is production-ready and released to be able to edit the complete look of your site.
The Block-based themes will have a number of extra options which streamline the process of creating a full site editing website and then being able to edit the entire website using blocks.
There are already a number of block themes such as Hansen, TT1 Blocks, or Tove. After the release of WordPress 5.9, there will be more themes supporting the FSE and have all of the site block elements which will make it easier to create and edit your site.
Some of the most popular WordPress themes such as Astra and Kadence will also support the full site editing in their upcoming releases. Using a block-based theme will contain a number of template parts and site blocks which will make it easier to use on your site. A number of the block-based themes also contain block patterns.