What is a placebo?
It is a treatment that does not contain any active substance but has the same appearance of a drug. For example, a capsule filled with sugar.
The placebo is needed because sometimes patients can start to feel better when they take a pill, not because the medication is working well but because they are being treated. By comparing a group of patients taking the drug with one who thinks they are taking the drug (the one who takes the placebo), doctors will be able to study whether the drug actually works or not.
Not all clinical trials include the use of a placebo.