This is a popular misconception especially among people with little knowledge of judaism. Judaism is quite different from other religions in this respect, because in practice, being jewish is usually not defined by personal religious belief but by genetic ancestry, they are jews by birth. By only analyzing the DNA of a human for example you can tell if that person is jewish or not with a very high probability. So while in theory it is correct that judaism is a religion, in practice it often makes more sense to consider jews as people with similar genes than as people with similar religious beliefs.
U.S., allies conduct 31 air strikes in Syria and Iraq against ISIS militants (Reuters)