A special element that can hold structural directives without adding new elements to the DOM.

The allows us to use structural directives without any extra element, making sure that the only DOM changes being applied are those dictated by the directives themselves.

This not only increases performance (even so slightly) since the browser ends up rendering less elements but can also be a valuable asset in having cleaner DOMs and styles alike.

It can for example enable us to use structural directives without breaking styling dependent on a precise DOM structure (as for example the ones we get when using flex containers, margins, the child combinator selector, etc.).