A caste system is a class structure that is determined by birth. Loosely, it means that in some societies, if your parents are poor, you’re going to be poor, too. Same goes for being rich, if you’re a glass-half-full person.
The phrase caste system has been around since the 1840’s, but we’ve been using caste since the 1500’s. You might’ve heard about the caste system in India, but there are caste systems all over the world, where people are born into a position, like having a certain kind of job, and it’s hard to change. America prides itself on not having a caste system, because people can “pull themselves up by their bootstraps,” and janitors can go to Harvard.