Homeopathy is a form of alternative medicine, which involves treating illnesses with severely diluted remedies (and common sense), first proposed by Samuel Hahnemann in the late 18th Century. Hahenemann observed that ingesting cinchona bark produced side effects similar to the symptoms of malaria and therefore prescribed it as a treatment for malaria. He then found that there are many other natural substances which produced side effects similar to the symptoms of known illnesses, so he conjured up the "Law of Similars" and decided that like must cure like. He believed that diseases were merely disturbances in a hypothetical "Vital Force" or "Life Force", and that mimicking the symptoms would stimulate the Vital force into expelling the original disease. These assertions have no basis in reality and would still have the same credibility if he had claimed that they were based on instructions written in unicorn blood on an invisible piece of parchment written by Jesus Christ reincarnated as a chameleonic Hypno-Toad.
The lack of common sense did not end there. He then decided that a normal dose would produce artificial symptoms but that a heavily diluted would actually cure it. He then created the Centesimal scale (C) to describe how much a substance should be diluted by a factor of 100. For example:
A 2C dilution requires a substance to be diluted to one part in one hundred, and then some of that diluted solution diluted by a further factor of one hundred. This works out to one part of the original substance in 10,000 parts of the solution. A 6C dilution is 1 part of the original solution per 1,000,000,000 parts of water. By this point, the remedy is almost indistinguishable from water, yet it is apparently more potent than the remedy. A 30C dilution (prescribed for many illnesses) is only one part of the original substance per 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 parts water. The homeopathic remedies for flue like illnesses can be 200C dilutions!
There is no scientific evidence for the purported efficacy of homeopathy. The only thing supporting ridiculous claims made this deranged form of alternative medicine is a whole host of anecdotal 'evidence' (a term I prefer to use rather loosely in this case).
This absurdity of homeopathy is highlighted in this Mitchell and Webb sketch - Homeopathic A&E.