You know your circulatory system keeps your blood moving, and your digestive system deals with the food you eat. But have you ever heard of your endocannabinoid system? The word looks like it has something to do with cannabis, the plant also known as marijuana — and it does. But why does this system exist, and what does it do? Answer: a lot. Whether you partake in pot or you've never touched the stuff, without a healthy endocannabinoid system, you'd be in a world of hurt.