How Cannabinoids Work and Why Are People So Interested in Using Cannabis?

How do cannabinoids act in the brain and body? And why are people interested in using cannabis to help with a range of medical indications? I think that maybe those two questions can go hand in hand, but they can also be answered separately. Now how is it that cannabis can be helpful for all these different indications that people might be using it? We're just starting to work this out at this point in time.