Template, slot, and shadow

mdn slot 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. 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

mdn slot login, 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..