What are the Ten Sefirot of Kabbalah?

“First, we must know the names of the ten Sefirot: KHB, HGT, NHYM. These are acronyms for Keter, Hochma, Bina, Hesed, Gevura, Tifferet, Netzah, Hod, Yesod, Malchut. These are also the ten coverings of His light, established so the lower ones can receive His light.

“This is like the light of the sun, which is impossible to look at unless through a darkened glass that diminishes its light and makes it suitable for the eyes’ ability to see. Similarly, had His light not been covered by these ten coverings, called ‘ten Sefirot,’ in which each lower one further covers His light, the lower ones would have been unable to obtain it.” — Kabbalist Yehuda Ashlag (Baal HaSulam), “Preface to the Sulam [Ladder] Commentary.”

What does it mean that the ten Sefirot are “also the ten coverings of His [the Creator’s] light, established so the lower ones can receive His light”?

It means that the lower ones, i.e., the created beings, which have to come out later in the process of creation from above downward, will have to receive the upper light (the Creator’s quality of love and bestowal), according to their desire to develop, and through the devices that the lower ones apply upon their desire, which are called “restriction (Tzimtzum), screen (Masach) and reflected light (Ohr Hozer).”

The upper light cascades down in gradations to the lower ones according to the latter’s proximity to the source of light. It is thus arranged such that from the upper source, the light gradually descends and enters the lower ones, which regulate their relationship to the desire according to the desire’s adaptation to the light.

The ten Sefirot are the ten coverings through which the endless light passes to the lower ones. These ten coverings are necessary so that the lower ones can adapt themselves to the upper light.