Element: slot property - Web APIs | MDN - MDN Web Docs

mdn slotSlots 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 usedelement .slot = aString. A DOMString. The definition of 'slot' in that specification. The slot property of the Element interface returns the name of the shadow DOM slot attached to the element. A