What did you already know about pejudice

the only thing i knew about Prejudice was, 'pride and prejudce' but i haven't read it yet or seen the movie.I asked this guy in my dorm and he told me that prejudice was what you think, or a theory. This thought or theory might not be true though. Prejudice occured when Hitler thought the Jews were the problem. Because Hitler thought this, he killed as many Jews as he could.