What is ''Azazel"?
Ramban #2 (citing the Ibn Ezra - and elaborating) 5 : It means that the goat goes - the goat represents Eisav, 6 who carries the sins of Yisrael out to his domain (the desert). In fact, the Sa'ir la'Azazel is in the form of a bribe to Sama'el, 7 the angel of Eisav, to dissuade him from prosecuting Yisrael on the day of judgment. 8
Perhaps this means 'rocky'.
As implied in Pasuk 22 (Rashi).
As a matter of fact, "la'Aza'zel is the acronym of 'le'Az Azal' - 'It goes to a harsh place. See also Ramban.
Since the Torah writes "el Eretz Gezeirah" (in Pasuk 22).
The Ramban's elaboration is based on a Midrash Rabah.
Indeed, the Pirkei de'R.Eliezer relates that, when Samael (who carried out all Yisrael's sins on the Sa'ir la'Azazel) sees that Yisrael are without sin, he exclaims in amazement how special are Hashem's people and how they resemble the angels - inasmuch as, on Yom Kipur, they go barefooted, they do not eat and drink, they remain standing, they are at peace with each other and they do not sin - just like angels!
What is the procedure of the lots?
Rashi and Targum Yonasan: Aharon places one of the goats on his right, the other, on his left; then he puts his hands into the box 1 (that is lying in front of him) and takes one lot in his right hand, and the other, in his left, 2 and places the one in his right hand, on the head of the goat on his right - and announces 'la'Hashem Chatas'; and the one in his left hand, on the head of the goat on his left - and announces 'la'Azazel'.
What is the purpose of the lots?
Ramban: Had Aharon decided on his own which goat is for Hashem and which goat is for Azazel, it would be akin to giving the former to Hashem, and the latter, to Azazel. 1 But now that he drew lots, it is akin to giving both goats to Hashem, and it is Hashem who gives it to Azazel. 2