Use this tag for question about HTML5 tag.
The <details>
tag is one of the HTML5 elements. It creates a disclosure widget and contains additional details, that the user can open and view. By default, the content of the tag is not displayed. In order to display the contents, you must apply the open attribute. A disclosure widget is commonly presented with a small triangle that twists (or rotates) to show open/closed state.
It is often used with <summary>
tag.