What exactly is the "placebo effect" and is it all psychological?
The placebo effect is a plain sugar pill getting rid of a ache, pain or sickness. This shows that many of the things we feel are in our mind. The brain is a very powerful tool. If you use it correctly you can get rid of a lot of the aches and pains you have and not have to take pain meds to help you.
Psychology: The power of expectations on experience of pain
Expectations have a lot of power over people as is evidenced by the placebo effect: Patients get pills that have no active ingredient. But the patients are not aware of that. Firmly believing that they are taking an effective drug, they actually get better afterwards. Only their expectations were at play here. Ref. Source 3y.