The component is child element rendering in a DOM node that exists outside of the parent component's DOM hierarchy (portal).

"Under the hood" ReactDOM.createPortal(child, container) is used with the ability to cancel the portal creation and to render the child component side by side in the parent. You can also specify the DOM-node to which you want to render the “children".

Example: select inside a modal window

<Modal>
  <Select disablePortal>Контент</Portal>
</Modal>

Or

const $ref = useRef(null)
<Modal ref={$ref}>
  <PortalProvider value={$ref}>
    <Select/>
  </PortalProvider>
<Modal>