Twenty Twenty-One Blocks is the name of the official Full Site Editing version of the upcoming default theme.
Twenty Twenty-One Blocks is an experimental theme created as an example to highlight what is possible with Full Site Editing.
The theme will need Gutenberg and the Full Site Editing experiment to be enabled. It will not be part of Core, but once complete it will be available in the theme directory.
During the theme creation process, the goal is also to help identify problems and limitations with Full Site Editing.
It is a unique opportunity to help shape