A butt plug does is exactly what it sounds like it does. It is designed to slide into your butt and stay put. There are many different kinds of butt plugs, and smaller can sometimes be better. They range form slim, to coned, textured, rippled, inflatable, the shape of the letter "T", beaded on a string and with and without vibration. They also have many different names like back door probe, anal intruder, anal beads, anal pearls, anal wands, and anal invader to name a few