Final answer:
Ordinary matzah is unleavened bread made from flour and water, guarded against fermentation from the time of milling, while shmurah matzah is guarded from the time of wheat harvesting, following stricter kashrut laws, and is preferred for the Passover Seder.
Step-by-step explanation:
The difference between ordinary matzah and shmurah matzah lies primarily in how each is guarded and prepared for consumption during Passover, an important Jewish festival. Ordinary matzah is made from flour and water, and care is taken from the time of the wheat's milling to avoid any fermentation; this ensures the dough does not rise, fulfilling the commandment to eat unleavened bread.
By contrast, shmurah matzah involves a more stringent process where the wheat is watched (shmurah meaning 'watched' in Hebrew) from the time of harvesting to prevent any contact with water until the dough is baked, to ensure total adherence to kashrut laws. During Passover, devoted adherents often prefer shmurah matzah for the Seder, the ritual meal that commemorates the liberation of the Israelites from Egyptian slavery.