Crisp flat breads called matzos are served at Pesach. They are a reminder of the Israelites who, in their escape to the desert, only had time to make flat breads, baked on hot stones. Instead of the two loaves of bread traditionally placed on the table during a festival, on Pesach, three matzos are served.
Because of the separation over the years of Ashkenazim and Sephardim, each group has evolved its own rules for what may or may not be eaten at Pesach. Ashkenazim forbid the consumption of corn, rice and beans (which are known collectively as kitniyot) for these can ferment and become yeasty. Sephardim, however, still eat these foods.