Incompatibilism is a very big word that refers to the idea that some things just can't go together. You know how sometimes you can't have a cookie and ice cream at the same time because your mom says you can only have one treat? Well, incompatibilism is kind of like that!
When we talk about incompatibilism, we're usually talking about the idea that people can't have free will and determinism at the same time. Free will means that you can make choices and decisions on your own, while determinism means that everything is set in stone and you don't really have a choice in what happens.
Some people think that free will and determinism can't coexist because if everything is already determined, then how can you really make choices? And if you can make choices, then how can everything be predetermined? It's kind of like trying to have a square and a circle at the same time. They just don't fit together very well!
There are other versions of incompatibilism, too. For example, some people think that moral responsibility and determinism can't coexist. If everything is predetermined, then how can you be responsible for your actions? It's like trying to blame a ball for rolling down a hill - it's not really the ball's fault, it was just going where the slope took it!
In conclusion, incompatibilism is a big word that means some things just can't go together, like free will and determinism or moral responsibility and determinism. It's like trying to have a cookie and ice cream at the same time when your mom says you can only have one treat - it's just not possible!