Jewish mysticism concerns the direct perception of God within the framework of Jewish belief and practice.
The "working" definition of Mysticism is 'a deeper understanding of reality'. Thus, Jewish Mysticism would refer to a specifically Jewish approach to the Ultimate Reality, based upon the revelation to each individual member of the Jewish People at Mount Sinai. The subject of Kabbalah is the study of "the body of The King" - the 'anatomy' of Existence, while Chassidus is concerned with creating a personal relationship with G-d.
Kabbalah means "received tradition" and a kabbalist must be able to prove an uninterrupted 'genealogical' line from student to teacher all the way back to basic seminal figures, paralleling the line of teacher-to-student ordination for rabbis, that goes back to Moses at Mount Sinai, and the biological genealogies of the Priesthood from Aaron or the Royal line from King David.
In the case of an essentially self-taught "outsider", like the Ari, who recast the Kabbalah in a 'new form' (debatable, since he harkens back to the 'dynamic' terminology of the Zohar and Sefer Bahir as opposed to the more 'structural' approach to the Kabbalah of Moses Cordovero and Nachmanides), the only way he could propound his innovations was after first submitting them to an acknowledged Master who would testify that the new approach was "like old wine in new bottles" and was totally in consonance with the traditions he had received from HIS master. The Ari submitted his system to Rav Chaim Vitale, and Rav Moshe Cordovero - the two leading Kabbalistic authorities of that time - who thereupon accepted the Ari as THEIR master! From that point on, the vast majority of Kabbalists have derived from the school of the Ari, which eclipsed all the other schools. Thus, all other schools of Jewish mysticism which were contemporary with him or came in contact with his teachings later- whether their emphasis was in meditation, prayer, or magic- recast their teachings in line with his.
Regarding prayer, though the older nusachs (rites) still exist, the law is that if one prays according to Nusach Ari, he cannot go back - 'One may ascend in holiness, but not descend to a lower level.'
Joseph Caro, who wrote the Code of Jewish Law, known as the Shulchan Aruch, which is the definitive arbiter of the Talmudic debates about the correct application of Jewish Law, was a disciple of the Ari. Since his decisions are grounded in the Kabbalah of his teacher, Jewish religious practice is an expression of kabbalah in action.
This subcategory deals with subjects where there is disagreement between recognized Jewish Kabbalists of this generation (please refer to the description for the Current Category), whether it be prophecy interpretation or moderns who claim prophetic powers, kabbalists with doubtful credentials, messianic movements, etc.
These claims need to be investigated by recognized Jewish kabbalists, as to their accuracy and truthfulness, before they can be put in another category.