Passover is the celebration of the freeing of the Jews from Egyptian rule around 3000 years ago. At the time, the Israelites were enslaved by the Egyptians ruler Pharaoh Ramses II. God instructed Moses to go to the Pharaoh and ask for freedom for the Jews. According to the Bible, his plea of "Let my people go" was ignored despite Moses' warning of punishments by God if the Israelites were not freed.
God then sent 10 terrible plagues upon the people of Egypt. The Pharaoh then conceded and freed eh Jews who immediately fled Egypt. They fled without taking time to bake their dough. They took the dough and baked it into thin crackers i the hot dessert sun. These crackers were called Matzoh.
To commemorate the freeing of the Jews, matzoh is eaten in place of bread during Passover.