Tzav means to command, and as the Parshah begins, G‑d tells Moses to command Aaron and his sons about how to do their job with the korbanot (which we began to discuss in last week's Parshah, Vayikra).

A fire must be constantly burning on the altar; it is the Kohen's responsibility to make sure it never goes out. The Kohen must clean the ashes from the altar every morning.

The first day that a Kohen does his service, he brings a mincha offering (of flour and oil) and the Kohen Gadol (High Priest) brings one every single day.

Parts of certain korbanot are eaten by the Kohanim, but they have to be eaten in the right time and nothing is allowed to be left over.

The laws of the korbanot that were explained in Vayikra are repeated here, this time to tell the Kohen what to do.

The Parshah now tells us of how Moses initiated Aaron and his sons to become Kohanim, as G‑d told him to do in Parshat Tetzaveh. First Moses put on Aaron his special clothing, and then he poured special anointing oil on the altar and on Aaron. Then he put on the sons of Aaron their clothing. Then Aaron and his sons brought a bull as a sacrifice upon the altar.

Then Aaron and his sons ate the meat from the korban and they remained for seven days in the Mishkan.