title: What does selector with brackets match? :not(a)[routerLink]
body: <p>This is a selector used to match <code>routerLink</code> directive.</p>
  
  <p>I know that <code>:not(a)</code> matches any element which is not an <code>a</code> element, but what does <code>[routerLink]</code> part mean?</p>