What is mentalism?
Mentalism is the study of other people's thoughts and minds based on their gestures and facial expressions. In short, it is mind-reading.
However, it is not mind reading as in occult. It uses psychology and human behavior to determine what a person is currently thinking of. All that is necessary for mentalism is a keen eye and observant behavior. And it is not as hard as one thinks. We do this on a daily basis.
For instance, a person like this o(^▽^)o would be happy. A person tapping their foot wants to leave a place. A person who blinks a lot tends to be lying. It is simple.
More on this topic should come on. Currently, I am taking in signals mainly from the hands and legs. The arms, shoulders, and face will come later, as those are the hardest sections to read the minds from.