Lens flare are unwanted artifacts caused by internal reflection and scattering of sun rays inside the lens. It appears when the sun is near or within the shot angle.
That’s it, have you been wandering in wheat fields during harvest? Or was it hiking on windy cliffs? Or you just use your gear a lot, and it gets inevitably dirty? Anyway you got visible specs of dust on your photos, and here are a few steps to get rid of it.
Did you know the human eye roughly has a 24-stops dynamic ? Well, that is about 2 times more than the best professional camera.
This explains why you are able to see more of a place where darkness and light combine with the naked eye than when you attempt to photograph it. A camera will require multiple exposures at different exposition parameters to render a highly contrasted scene. This is what HDR (High Dynamic Range) photography is all about.