There are many types of sacrifices in the Old testament, and it is notable that the earliest kind mentioned in the Bible is the bread and the wine offered by Melchisedech.
Leviticus 17:11 Since the life of a living body is in its blood, I have made you put it on the altar, so that atonement may thereby be made for your own lives, because it is the blood, as the seat of life, that makes atonement.
Hebrews 9:22 According to the law almost everything is purified by blood, and without the shedding of blood there is no forgiveness.
There were also different kinds of offerings:
*]Holocausts (burnt offerings)
*]Communion sacrifice of peace offerings
*]Sin and guilt offerings
Here are a couple of theories about the offerings:
*]These sacrifices are a gift of appeasement to a cruel and demanding deity. (There is really no evidence to support this theory from the Bible)
*]The sacrifice was a kind of bilateral contract in which the people gave a gift to God and God reciprocated by granting them something in return. (But this theory implies God had need of the gift, which is foreign to Biblical thought)
*]Or the sacrifice is a meal shared with a hungry God. (Of course, this is rejected by Psalm 50:12-13 “If I were hungry, I would not tell you; for mine are the world and its fullness. Do I eat the flesh of strong bulls, or is the blood of goats my drink?”
Here is a qote from the New Jerusalem Bible Commentary. 76:93
Sacrifice was a gift, but a gift to which God had an imperative right, since anything that people could offer had first come from the bountiful divine hand. “The Lord’s are the earth and its fullness; the world and those who dwell in it” (PS 24:1, also 50:9-13; 1 Chr 29:14).In returning a part of God’s property to him, people symbolically acknowledge God’s right to it all, and thereby acquired a right to use the rest of it, under God, for their own purposes. This was the idea behind the offering of the firstfruits and the firstborn. From another point of view, since the offeringswere staples (meat and vegetables) by which people sustained their lives, the victims represented the life and being of the one offering. In sacrificing, a person symbolicaly surrendeded to God; and God, by accepting, bound himself in some way. It was not a quid pro quo notion, since God had no need of the gift and there could be no proportion between the gift and God’s favor.
The essense of the sacrifice did not consist in the destruction of the victim. In fact, in the case of animal sacrifices, the slaughter of the victim was only a preparatory rite and was performed by the offerer, not by the priest. One reason for the destruction of the offering, whether animal or vegetable, was that it made the gift irrevocably definitive and withdrew it completely from ordinary use. Also it rendered the victim invisible and symbolically sent it into the invisible sphere of the divine. The word fo holocaust, “ola”, means basically “that which goes up.” The ritual served to symbolizethis idea of “giving,” of “sending up” to God. The altar was the symbol of God’s presense; and the victim’s blood, the most sacred element, was brought into direct contact with this symbol. In every sacrifice, the blood was poored out at the base of the altar…The sacrifice, then served as a gift expressing the Israelite sense of dependence on God, but it also indicated the desire for union with God. The Isrealites never enteretained a crassly physical notion of this union; theirs was a more suble attitude, in harmony with the sulime spiritual transcendence of Yahweh. When God had received his share of the victim, the ones who had presented it ate the remaineder in a sacrificial meal. The fact that one victime had both been offered to God and eaten by the worshipers brought the two parties together in a spiritual communion, establishingand consolidating the covenant bond between the two. This was a joyful occasion and in the early days the communion sacricfice was the most popular of rituals.