I'm learning responsive design. (Make width <500px and see)

I'm talking about this line:

.dropdown, .subdropdown {

    position: static;

    width: 100vw;

  }

This is the behaviour I'm getting with and without position:static. But I fail to understand why? All information that I've about position:static is that it doesn't accept Top,Bottom,Left,Right values.

My teacher say "it is floating without static...normal flow of document" but I don't get it.