A placebo is often called a “sugar pill” since this is its original meaning. It refers to a product or treatment that is known not to have any efficacy to treat a certain condition.

In order to test the efficacy of a medical treatment, a group of patients is treated with the treatment, while another group of patients is treated with the non-treatment (placebo). If the treatment group fares better than the placebo group, the new treatment has a genuine chance of becoming an officially accepted treatment.

One aspects of placebo is the so-called “placebo effect”, an effect that is no well understood by the general public. A certain percentage of people will be cured, even when not treated at all or when treated with a placebo. These people find it often impossible to understand that the treatment did not do anything for them, and will maintain that it cured them.

Confusing correlation with causation, these people often feel that whatever therapy they received, genuinely cured them. This is the way that essentially nonsensical treatments, such as prayers, homoeopathy, magnetism and so many others can remain popular, even when they are known not to work.