The HTMLDetailsElement interface offers additional attributes for manipulating <details> elements (in addition to the ordinary HTMLElement interface that is also made accessible to it by inheritance).
An interactive widget that the user can open and close is frequently made with the <details> tag. The widget's default state is closed. It expands upon opening to reveal the contents.
Any sort of content can be put inside the <details> tag.
Tip: A visible header for the details is specified by using the <summary> tag in conjunction with the <details> tag.