Acharei Mot - Sheini
Out of Order
The Kohein Gadol would mix the blood of the bull with that of the goat and place some on the horns of the altar, then sprinkle seven times. Then it was time for the goat "for Azazel," better known as a "scapegoat" (from which we derive the term).
The Kohein Gadol pressed his hands on the scapegoat's head, metaphorically imbuing it with the people's sins. A designated messenger would then lead the goat to the wilderness.
At this point, the Torah tells us that the Kohein Gadol would enter the Mishkan, take off his linen clothes, and leave them there. He would then immerse in a mikvah, and put on his regular uniform. However the Talmud in Yoma 32a clarifies that this sequence (specifically verse 23) is actually out of order. The Kohein Gadol clearly didn’t change clothes in the Mishkan. He re-entered the sanctuary to retrieve the utensils left there from the incense service, then changed clothes. (The Torah doesn’t go in strict order so that all the relevant parts of the service would be discussed together.)
The Kohein Gadol would then offer two burnt offerings, his own and the people's.
So... what's this Azazel? While there are different opinions as to the exact etymology of the word, it is generally accepted that it refers to the wilderness where the goat was taken, possibly the name of a particular mountain. The Talmud in Yoma 67b says that it’s a rocky cliff in treacherous terrain. But by no means was Azazel the name of another power (G-d forbid!), so don't be mistaken!