The Common category includes the following blocks: Paragraph, image, headings, list, gallery, quote, audio, cover, video.
The paragraph block is the default block type. It should not have any alignment of any kind. It should just flow like you would normally expect. Nothing fancy. Just straight up text, free flowing, with love.
This paragraph is left aligned.
This italic paragraph is right aligned.
Neither of these paragraphs care about politics, but this one is bold, medium sized and has a drop cap.
This paragraph is centered.
This paragraph prefers Jazz over Justin Timberlake. It also uses the small font size.
This paragraph has something important to say: It has a large font size, which defaults to 36px.
The huge text size defaults to 46px, but the size can be customized.
This paragraph is colorful, with a red background and white text (maybe). Colored blocks should have a high enough contrast, so that the text is readable.
Below this block, you will see a single image with a circle mask applied.
Cover block with background image
The file block has a setting that lets us show or hide a download button with editable text:
Video blocks have settings for showing and hiding the playback controls. Use autoplay and playback controls responsibly.
The video block below is muted and has a poster image that displays before the video starts:
Posted as per the instructions in the Codex.