WordPress 5.0, released in December 2018, introduced the Block Editor ( aka Gutenberg ). The Block editor is used to create and manipulate Blocks. WordPress provides a starter set of Blocks, which are extensible. Plugins and themes can add their own.
We’re starting to build a new catalog of Blocks, intended to be similar to the Shortcode catalog.
The core blocks for WordPress will be created in /blocks. Other sites will initially point you to these blocks.
I’m currently attempting to build the infrastructure to allow blocks for other plugins and themes to be discovered.