Template, slot, and shadow - web.dev

mdn slot We'll discuss using the template> and slot> elements, the slot attribute, and JavaScript to create a template with an encapsulated Shadow DOM. We'll then re-use. An element with a slot attribute is assned to the slot created by the slot> element whose name attribute's value matches that slot attribute's value.

mdnslot, Learn about the Element.slot property, including its type, code examples, specifications, and browser compatibility..