<details> … </details> | The HTML Details Element (<details>) creates a disclosure widget in which information is visible only when the widget is toggled into an “open” state. |
<summary> … </summary> | The HTML Disclosure Summary element (<summary>) element specifies a summary, caption, or legend for a <details> element’s disclosure box |
Example
<details>
<summary>Details</summary>
Something small enough to escape casual notice.
</details>