Kosher bread has been prepared according to the kashrut, which is a set of dietary rules found in the bible. The kashrut also sets out how the foods can be prepared, which foods can be eaten together, and which combinations are to be avoided. Kosher bread has packaging that is marked with a kosher stamp to indicate that it has been prepared according to the strict guidelines of the kashrut. The three basic concerns regarding bread are the ingredients, the equipment used to prepare the bread, and some additional rules that only pertain to bread.
When preparing kosher bread, all of the ingredients must be kosher. Wheat is by its nature always kosher, with no special considerations needed. Some very conservative Jews follow the practice of not eating wheat before a special sacrifice call Omer on the second day of Pesach. Bread that adheres to this rule is labeled as Yoshon. Since most breads are baked with animal fats and yeast, a rabbi must be present to ensure these and any other ingredients are kosher.
Utensils used to bake kosher bread cannot have been used to make foods that are not kosher. If they were used for something non-kosher, they have to be kashered, or cleansed in the proper manner using a high heat. The utensils are then ritually purified by a rabbi. Kosher bread also cannot be prepared on one of the holy days or the sabbath.
According to Jewish law, a small portion of bread, about the size of an olive, should be broken off when the bread is either in raw form or baked. This small piece is called the challah. The challah is then burned by throwing it on the floor of the oven, after which it is thrown away. This ritual is only performed if the baker, or owner of the dough, is Jewish. If this traditional ritual isn't performed in the bakery, it can be performed at home before the bread is eaten to ensure the bread is kosher.
Passover is a Jewish holiday that commemorates the exodus of the Jews from slavery in Egypt. Moses instructed the Jews to depart quickly, causing them to leave without time to allow the bread to rise. During passover, the only kosher bread is unleavened bread. Jews eat matzo matzo, an unleavened, cracker-type of bread, to remember this hasty departure, and are prohibited to eat anything with yeast.