Answer:
   
   They came from different cultures, and so particular customs developed
   differently, such as details of the prayer service and permitted foods
   on Pesach. The [5]Shulchan Aruch by R' Joseph Karo is the definitive
   Sephardic work on halacha, and R' Moshe Isserles later added glosses
   to describe Ashkenazi practice. Other works describe the customs and
   practices of particular communities.
   
   Many of the customs (minhagim) are derived from the communities in
   which these groups arose. The customs of Ashkenazi Jews often resemble
   those of the Slavs and Germans, because the Ashkenazi Jews were
   concentrated in that region. Additional information may be found in
   Paul Wexler's book The Ashkenazic Jews by Slavica Publishers.