"Portrait" or else ...
Orientation applies to many topics. In the information age it usually refers to how one's display is oriented. The choices are Landscape (LS) or Portrait (PT). In LS the display width is greater than height. The opposite is true for PT.
Display attributes include sound, images, and language elements. Image and language characteristics include size, shape, color and motion. Content diversity runs from the evening news to database searches. To an extent, content type suggests orientation. The artist or designer had specific content and orientation concepts.

The "Surf" illustrations show macro and micro advantages of each orientation. All Diego Rivera's works are not LS. Should one start with the big picture or small details?

APS may be designed to sense your disp[ay orientation and deliver optimized pages. See the "Chateau de Laurel" examples. Some APS are designed primarily for an orientation. Just because your mobile device  (phone) allows you to change orientation it doesn't guarantee a pretty result.
Be flexible, smell the roses. Unlock "Display Orientation." Try looking at things both ways. One orientation doesn't fit all! And, BTW, leave the sound on, hard to tell what you're missing.