Prosphora is Greek for "that which is offered"; it is a type of round leavened bread used for communion and liturgical ceremonies by Eastern Orthodox Christians, particularly in Greece and Russia. Its use stems from a variety of religious traditions. St. Justin recommended that, after seven days of showing penitence by eating unleavened bread, worshippers symbolically adopt a spiritual fresh start to their lives by eating new leavened bread.
There are various recipes for creating prosphora; most involve just water, high-gluten wheat flour, yeast, and salt. Some recipies call for the use of holy water. Depending on the rules of the parish, a priest may need to bless the cooking area before the bread can be made. Before the loaves are baked, the baker presses a seal into the dough to create a religiously-significant design in the top of the bread.
Priests or designated laypersons can make prosphora. Families can make the bread for special occasions such a funeral, but a priest must bless the bread before it can be eaten.
In the Proskomidia (the Orthodox version of the Offertory) the prosphora is cut up to be served to worshippers in a fairly complex ceremony that pays tribute to the sacrifice Christ made during his crucifixion. The loaf of bread symbolically takes the place of a lamb as a sacrifice to God. Small slices of bread (called "particles") are laid aside as offerings to Christ, the Virgin Mary, the Angels, the Prophets, the Apostles, the holy Hierarchs, the martyrs, Christ's ancestors, and other saints who relate to the services being performed that day.