Will I receive the actual treatment or a placebo?
It depends on the study design. Some studies have no placebo at all (single-arm, open-label studies common in oncology and rare disease). Others use placebo controls — usually in conditions where no effective standard treatment exists, or where the placebo is added on top of standard care so no one is denied known-effective treatment. In a typical placebo-controlled randomized trial, you have a roughly 50/50 chance of receiving the investigational drug versus placebo, and neither you nor your immediate care team knows which (that's 'double-blind'). Even on placebo, you receive the same monitoring, the same visits, the same labs, and the same standard care for your condition. After the study ends, sponsors often offer an 'open-label extension' where everyone — including former placebo participants — can receive the investigational drug if it proved effective. The study design, including placebo use and probability, is always disclosed in the informed consent form.