slot>: The Web Component Slot element - webdocs.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. When the slot's containing component gets rendered, the slot is rendered with the custom element's child that has a matching slot attribute. A named slot is a slot> element

mdnsport login, Slots are identified by their name attribute, and allow you to define placeholders in your template that can be filled with any markup fragment you want when the element is used.