We compare the response to a treatment to:
A control is a situation where no treatment or a standard treatment is administered. It serves as a reference mark for the treatment being studied. (e.g., a group of subjects does not receive any drug or pill of any kind, or receives the current prescribed treatment).
A placebo is a fake treatment, such as a sugar pill. This is to test the hypothesis that the response to the actual treatment is due to the actual treatment and not the subject’s apparent treatment.