Dividers are just hr tags.
Example
This is a paragraph with a divider after it.
This is a paragraph after the divider.
Styling
Style hr tags.
Divider
This page is generated from a page in Notion database, and is intended to demonstrate the capability of the Divider block.
You can view this page in Notion to see that it corresponds well to what is displayed.
You can pick a stylesheet below to change how it renders.