Usually when you're taking a portrait photo of two people and one of them is significantly taller, you'd get something like an apple box for the shorter person to stand on. But what if there's nothing on hand? To adjust the taller person's height without hunching over, have them spread their feet apart.
As photographer Peter Hurley demonstrates in this video, the taller person doesn't have to awkwardly hunch down to be on the same level if they just spread their legs apart. Yes, it looks completely goofy so this only works if you're shooting their portrait from the waist up, or if you crop the photo later.
But it's an easy way to address a height differential that would otherwise make for a tricky pose.