Built-in special attributes is

Used for binding dynamic components.

There is, however, a use case where you may need
Vue to replace a native element with a Vue
component, as explained in in-DOM Template
Parsing Caveats. You can prefix the value of the
is attribute with vue: so that Vue will render
the element as a Vue component instead:

<table>
  <tr is="vue:my-row-component"></tr>
</table>