Santeria is all about the relationship between humans and orishas. Humans seek the counsel and favor of the orishas, but the orishas also need a life-giving power known as ashe to survive, and they can only receive it through the offerings made by humans. There's a great many sources of ashe, but it is best released through burning and blood. Thus, many offerings are burned, and animal sacrifice with focus on the draining of blood is a standard practice among believers. These offerings of ashe to the orishas is known as ebbos.