Question:
What is homeopathy? What is the history of the discovery and use of homeopathy?

Answer: I wouldn't exactly call it *ancient* since it's only 200 years old and Dr. Hahnemann didn't discover it--he developed it.

Homeopathy is based on the use of extremely dilute preparations of botanical, animal or mineral substances. Homeopaths believe that these remedies work to stimulate the body's natural immune response. Homeopaths believe that this is only one true disease--imbalance--and that the cure for all disease is to bring harmony back to the body through the stimulation of the body's natural healing mechanism.

The problem with homeopathy (and why it's so violently ridiculed by scientists) is that the remedies are so dilute that some doses of the remedy exceed what we call the Avagadro limit. In other words, some doses won't contain even a single molecule of the "active" ingredient. Homeopaths explain this by saying that the active ingredient need not be necessary in every single dose because the manufacturing process spreads the "healing power" throughout the remedy in some process they can't fully explain.

That's the 25 cent version. It's a little more complicated than that, but that's the gist of it.