Think for a moment about the screen image you see looking at your smiling face about to snap a selfie. Now compare that first, screen image to the actual photo that gets stored when you snap the selfie. Both are you; but they are not exactly the same!
The first screen image is reversed in the saved photo image. The first image is just like looking at yourself in the mirror. The saved image is the reverse. The first image is the one we know best; it is the most familiar to us. We've been looking at it for years.
But other people see us in reverse. They see, in effect, the saved photo image. We see the mirror image; we've conditioned ourselves to see it whenever we brushed our teeth or adjusted ourselves in front of a mirror.