Ashkenazi (from the name of one of Noah's grandsons) is a Jew of eastern European or German descent; as compared with Sephardim, refers to the group of Jews who, after the diaspora, settled in central and northern Europe. Many famous Jews are Ashkenazi (which is both a noun and an adjective), Albert Einstein among them.
Ashkenazi Jews follow many different practices than Sephardim. For instance, Sephardi Jews eat rice on Passover, but Ashkenazi Jews do not.