There are many types of marbles, mostly made out of agate, glass, clay or steel. They can be used as toys for children, or even as collectables, selling at conventions or auctions.

While some are made out of real marble, "alley" is short for alabaster, which is more translucent and softer than marble itself. The term "snake" refers to the colored pattern on the marble, so an alley snake is a whiteish alabaster marble with a splash of color snaking through it. There are many possible combinations of streaks and waves and patterns of color with fancy names like corkscrew, ribbon, spirit, swirl, onyx, butterfly and bumblebee.

Former marble players often become collectors of these beautiful little spheres, both for their nostalgia and their amazing colors.

More Info: en.m.wikipedia.org