Ah, yes, one of those. That is a little doodad that once upon a time served a purpose as part of a complete mechanism of some sort, such a bicycle. Someone came along and separated all the constituent parts of that mechanism, presumably with the intention of maximizing its value. But when he got to this little doodad, separated from the rest of the mechanism, he could no longer identify it. So he turned to the internet.

You may say, of course, I just made that little story up. And you are right. But it has happened many times before.