Slippers are shoes that are designed more for comfort and warmth than for protection. They are for indoor use only. They usually have a flat sole (no raised heel), and often have little or no back, just covering the toes. they They often have strange designs, sometimes being as much a stuffed animal as a shoe. On the other hand, some slippers are simple and subdued. Whatever your personality type, there's a slipper for you.
In fairytales and other old stories the females often wore slippers, which were designed for looks. I doubt that comfort, warmth, or protection was taken into account at all. These were most likely made so that rich women could show off the fact that A. they were rich, and B. they didn't have to have functional shoes, because they didn't have to do real work.
In many parts of the world, what I would call flip-flops are called slippers. These are nothing but a flat sole with a Y-shaped strap, with the base of the Y between the big toe and the other four toes, and two arms attached to the sole halfway back along the foot. Great beachwear.