The term Ein Sof is sometimes taken in Kabbalah to refer to God's very essence (in which case, of course, it precedes the previous entries of this synopsis).
When more precisely used, however, Ein Sof refers to God's infinite light, before the beginning of the creative process. Ein Sof = 207 = Or ("light"). Were Ein Sof--literally "no end"--meant to refer to the essence of God, it would be more appropriate to call Him Ein Techila--"no beginning" ("no end" implies a "beginning" which precedes it, but, certainly, nothing precedes God). The infinite light which emanates from God's very essence does in fact possess a beginning (God's essence) but does not possess an end.
Even more precisely, Chassidut teaches (in the name of the Maggid of Mezritch) that Ein Sof refers to the infinite light generated by the malchut of Echad. The thought and desire of Ana Emloch (as described above) resulted, spontaneously, in a "surge" of infinite energy and light to enact the creative process (just as the heart of a mortal king becomes full of "infinite" energy and light to materialize his will to rule).
The relation between Ein Sof and the power of malchut is indicated by the fact that Ein Sof = Adon Olam ("the Master of the universe"; Ein = 61 = Adon, Sof = 146 = Olam). In the beginning of our daily prayers we praise God as: "The Master of the universe Adon Olam who ruled before any being was created."
The surge of infinite energy and light, Ein Sof, is referred to in the Zohar as the Tehiru Ela'ah, the "higher brilliance" (in contrast to the Tehiru Tata'ah, the "lower brilliance," which appears after the initial contraction of God's infinite light, as will be explained).