Everything isn’t backwards in mirrors, it just seems backwards from your perspective. Mirrors work when photons, particles of light, stream towards the glass and bounce off it. The image of everything in front of the mirror is reflected back along the path it came. If you wore a glove on your right hand, the glove would still be on your right hand in the mirror. However, if you wrote a word normally on a sheet of paper that you could read perfectly well in front of your face, you would have to turn it around to face the mirror. It then appears as if the writing is backwards, but it’s actually you that turned it around, not the mirror. If you wrote a word normally on a clear piece of plastic and turned the plastic around, the word would appear backwards too.