With the Markdown block you can create formatted content using only regular characters and some punctuation marks. Markdown is used by writers and bloggers who want a quick and easy way to write formatted text, but without having to take their hands off the keyboard, and without learning a lot of complicated codes and shortcuts.
The Markdown block is enabled by default when you set up Jetpack.
Since it is a block only, it remains available even if you disable the Markdown feature in Jetpack → Settings → Writing → Composing.
Adding a Markdown block
You can add a Markdown Block to any post or page, by selecting it from the Jetpack section of the block picker: