It's lens flare. I'm an enthusiast photographer and this happens all the time with a really bright subject in frame, such as light bulbs or the sun. It also can have the effect of lowering contrast in a photo, as you can see what is almost the appearance of a haze on their suit jackets.

Camera lenses consist of multiple lens groups, not just one lens. As such, light passes through multiple lenses before reaching the camera sensor. Curved lenses suffer from refraction as light passes through their curved surfaces.