The WordPress Block editor introduced in WordPress 5.0 was originally developed as a feature plugin called Gutenberg.
Blocks are the fundamental element of the editor. They are the primary way in which plugins and themes can register their own functionality and extend the capabilities of the editor.
Blocks for oik plugins
For oik-plugins all blocks are currently being developed in the oik-blocks plugin.
Total amount of Block related content you’ll find in this site:
WordPress provides 35 core blocks for creating content in your own site and over 30 blocks for Embedding content from other sites.
Many other plugins and themes have started delivering their own blocks.
Yoast SEO, Jetpack, WooCommerce