"Yetsirah" as in "making" is as opposed to "Briah" as in "Creating": actually taking whatever matter that was created in the "Briah" and shaping it into the basic elementsThe World of Yetzirah, "World of Formation" contains ten sefirot which are still further removed from Deity, and thus of a less refined nature than those of the World of Briah. Yet they are still non-material. This is the abode of the angels, who are wrapped in luminous garments. The myriads of angels are divided into ten ranks, according to the ten sefirot, and each angel is set over a different part of the universe, and derives his name from the element or heavenly body he guards.
This region is interpreted in the Zohar as the world of the lower heavens, consisting of the seven planetary firmaments
