hi Captain_Brain,
-Rei means "the universal life force" and ki :"the force that binds everything together". (Ki is the same as qi or chi). In other words, it is the energy of all that is/lives.
-Reiki is a healing method. It works with energy. You don't give your energy, as physic healers do. You are only a link between the person you want to help and the universal energy.
-It was developped by Mikao Usui (Japanese) in the 20th Century, but it comes from Tibet and it is very old.
-it works with symbols. Those symbols are tools that will help you concentrate and direct the energy.
-Reiki is not a religion.
-if you've googled it up a bit, you might have heard about attunements. I think they are necessary on a psychological ground only (that's the same for reiki symbols I guess), and that everybody can do reiki, attuned or not. I think people need the attunements in order to be convinced they can do reiki. Shakespeare said "life is a theater". People need theater...some reiki masters take advantage of it and they charge their pupils more than necessary. But other reiki masters will attune you for free.
Any questions?