The Raspberry Pi credit card-sized ARM computer was invented as a means for students to learn how to program hardware and software. It quickly became a very popular item though.
In fact, it became so popular that the Raspberry Pi Foundation just had to revise it, then release new versions of it, all the while having trouble getting enough for everyone.
What we have here is another so-called revision, named Raspberry Pi Model A. If possible, it is an even more slimmed-down version of the ARM-based Linux computer.
It uses a third of the energy consumed by Model B and has 256 MB RAM and a single USB port.
It is cheaper too. While model B made a name for itself with better hardware at the same price as before, this one is cheaper, at $25 / 18.42 Euro / 19 Pounds. Go here for the whole scoop.