Antisemitism is when someone does not like Jewish people and may even want to hurt them or take away their rights. It dates back very far in history. People have felt differently about Jews for thousands of years, maybe because they are different, or because they believe different things, or even because they look different. Some people found that they could use antisemitism (hating Jewish people) to blame Jews when something bad happened or to get other people to follow them or agree with them. Over time, this has caused a lot of pain and hurt for Jewish people, who were discriminated against and treated unfairly.