Compositing otherwise unrelated photos means to take two or more images and turn them into one. Deceive the eye. In short a study of light and color, with strong Photoshop skills is what is developed.
In choosing two photos to composite perspective, horizon line, and lighting are imperative to match initially to ensure a quality end result. By using an array of PS adjustment layers the final result is achieved.
Sometimes you just go crazy and use seven photos, merging them into one. An oversized boy fishing off a lighthouse with a gummy worm for Swedish fish. I call it "To Fish as a Kid Again".
I call the above "Space to be Loud"
I call the above "Hang in There"
I call the above "Stay Calm"