There are several types of sacrifices that are used in the Holy Temple to create high spiritual connection and draw Light to the world.
Rabbi Ashlag explains that Malchut (female, Eve) was taken from Zeir Anpin (Male, Adam) so Zeir Anpin is not complete until Malchut comes back. This is true for all the inner Sefirot of Zeir Anpin. Without a unification with Malchut, the Light cannot come into the vessel.
The sacrifices elevate Malchut to Zeir Anpin for a unification that brings completion of the vessel and the Light flows down and nourishes Malchut.
Daily Zohar # 2083 – Tzav – Sacrifices for Light