Rule of thirds, Leading lines, and depth of field.

Image Source: https://atavi.com/browser-themes/p/green_waterfall/chrome-themes-top

Top three blocks show the sky in a decent focus. The middle row shows the top and the body of the waterfall and towards the left it starts to become more blurry , which is why i think that this photographer used a medium depth of field. Lastly the bottom three squares show the body of water frozen in motion.

photo by Antoine Beauvillain https://contrastly.com

These red lines show a railroad track going on through the screen till it is blurry and not visible.

Image Source: https://viewbug.com

The dog on the inner red line is in focus while the background, due to shallow depth of field is blurry and unfocused.

In this picture the dirt walkway and the trees lead the eyes towards the center.

In this picture the horizon is the top third, the mountains are the middle and the trees are the bottom three of the line.

In this picture the berries stay in focus while the background is blurry.