Reverse smoking is when you smoke a tobacco pipe backwards - this means that instead of lighting up and smoking the end of the pipe that's closest to your mouth, you light up and smoke the end that's furthest away from your mouth.
But why would anyone do this? Well, some people believe that reverse smoking has health benefits - specifically, that it's less harmful to your lungs than normal smoking. This is because when you reverse smoke, the smoke is cooled down by passing through the long stem of the pipe before it reaches your mouth, which supposedly makes it less harsh on your lungs. It's also said that reverse smoking can help to prevent tongue bite (a painful burning sensation on the tongue that can be caused by smoking) because the tobacco doesn't come into contact with your tongue as much as it does when you smoke normally.
However, there's no scientific evidence to support these claims - in fact, some experts believe that reverse smoking might actually be more harmful than normal smoking because it can lead to more condensation and moisture build-up in the pipe, which can in turn lead to mold and bacteria growth. So while reverse smoking might seem like a fun and unusual way to smoke, it's probably not a good idea if you're concerned about your health.