Kabbalists believed that there is a gap between how mankind can understand God and what God actually is. This unknowable aspect of God is called Ein-Sof.
Mysticism involves attempting to communicate with or directly experience the divine. Monks and nuns have often used meditation and prayer to induce mystical states but it can also involve esoteric practices like kabbalah. Read articles about mysticism below.
Mysticism is not new to Judaism. It dates back at least to the 6th century BCE with Ezekiel’s visions of the divine chariot (called merkavah mysticism) in Isaiah. In the year of King Uzziah’s death I saw the Lord sitting on a throne, lofty and exalted, with the train of His robe filling the temple. …
During the 15th-16thc. in Europe, many of the great occultists - Marsilio Ficino, Pica della Mirandola, Henry Cornelius Agrippa, and John Dee - flourished.