Block category: Common
The Common category includes the following blocks: Paragraph, image, headings,...
Block category: Embeds
This post tests various embed blocks: https://twitter.com/WordPress/status/1057136472321613824 Twitter, wide width...
Media: Twitter Embeds
https://twitter.com/nacin/status/319508408669708289 This post tests WordPress' Twitter Embeds feature.
Post Format: Video (WordPress.tv)
https://wordpress.tv/2009/03/16/anatomy-of-a-wordpress-theme-exploring-the-files-behind-your-theme/ Posted as per the instructions in the Codex.