Pug not only allows you to use string interpolation but also tag interpolation. It is a convenient feature if you want use a tag inside text of your tag

p.
  This is a very long and boring paragraph that spans multiple lines.
  Suddenly there is a #[strong strongly worded phrase] that cannot be
  #[em ignored].
/*
<p>This is a very long and boring paragraph that spans multiple lines.
  Suddenly there is a <strong>strongly worded phrase</strong> that cannot be
  <em>ignored</em>.</p>
*/

I create a video if you prefer learning by watching

https://youtu.be/1OzYYpyVkfs