David Ariel, in his book Kabbalah: The Mystic Quest of Judaism, argues that mysticism is a form of religion that connects with G-d just outside rabbinic observance (halacha). In this sense Kabbalah Ma’asit exists at the outer limits of the rabbis’ “fence around the Torah.”
The kabbalistic view of G-d as Transcendent, Unknowable, Unreachable and Inconceivable – denoted Ein Sof (“the infinite”) – is not the classical divinity of the Bible and rabbinic literature. To reach this unknowable G-d the spiritual traveler must set forth upon a mystical passage through the ten sefirot, the attributes of G-d through which He is reachable. This is an extremely complex path requiring years of study. The sefirot thus mark out a grand spiritual journey through the unified but “internally changing” nature of the infinite transcendental G-d as explained in Kabbalah.
The sefirot are often graphically illustrated, and the Ilanot Hakodesh (“holy trees” or “trees of life”) are usually elaborate renderings on a very large scroll of vellum. These represent one facet in the grand scheme of the theoretical Kabbalah Iyyunit. On the other hand, we have similar scrolls graphically arranged with the order of the sefirot, but these serve as amulets which also include the holy Names of G-d and His angels and demons and are usually made for a specific individual. These quasi-Ilanot are expressions of Kabbalah Ma’asit, practical Kabbalah. In the midrash Shemos Rabba 3:6, we read, “The Holy One, may He be blessed, said to Moshe: ‘You wish to know My Name? The Name by which I am called depends upon my work.’” The magic Names invoked in the amulets serve for healing, against the Evil Eye, for good luck, for childbirth, against epidemics, etc. The demons named on amulets are generally cursed and to be repelled. The most important and most quoted Name on amulets is that of the Almighty, due to His tremendous power. First in importance is the Tetragrammaton (Greek for “a word of four letters”), the secular designation for the most holy and ineffable Name, yud, kay, vav, kay.
Magic and mystical practices were a normal feature of Jewish life in both Ashkenazi and Sephardic communities alike. This was through the so-called “practical” Kabbalah, in the writing of amulets on paper, parchment, silver, and even base metals such as iron and brass.
More can be found in perhaps the best introductory work on Jewish Name magic, The Hebrew Amulets by Theodore Schrire.