A placebo is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills)...
https://en.m.wikipedia.org/wiki/Placebo
Not to say Wikipedia is infallible. I'm sure it's not. Just checking how clueless I am and the internet suggests my understanding is "common knowledge."
Perhaps you can share more of your knowledge about what placebo pills typically contain and enlighten us? (Citations welcome should you choose to share.)