What's the difference between "Portrait and Landscape" and "Portrait" or "Landscape?"

Here's a guide that I got from https://css-tricks.com/snippets/css/media-queries-for-standard-devices/. Part of his resource has this:

/* ----------- iPhone 5 and 5S ----------- */

/* Portrait and Landscape */
@media only screen
  and (min-device-width: 320px)
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2) {

}

/* Portrait */
@media only screen
  and (min-device-width: 320px)
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: portrait) {
}

/* Landscape */
@media only screen
  and (min-device-width: 320px)
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: landscape) {

}

What's the difference between having a setting that's being prescribed for "Portrait and Landscape" as well as "Portrait" and "Landscape?" It seems like that "Portrait and Landscape" setting expects the user to be able to see the screen in two different resolutions at the same time, and I know that can't be right.

Can someone explain this to me?