The Jewish mystical doctrine known as "Kabbalah" (="Tradition") is distinguished by its theory of ten creative forces that intervene between the infinite, unknowable God ("Ein Sof") and our created world.
Through these powers God created and rules the universe, and it is by influencing them that humans cause God to send to Earth forces of compassion or severe judgment.
The right side represents the principles of unity, harmony and benevolence, as embodied in the Sefirah of Hesed. It is associated with the bestowing of generous goodness upon our world. It is the masculine side.
The Left side of the Sefirot structure is the side of power and strict justice, the values embodied in the Sefirah of Din. It is the female side, representing the fearsome awe of God, and the principles of separation and distinction. The unrestrained dominion of the Left side gives rise to Evil.
The Middle column of the Sefirot structure represents the ideal balance of divine mercy and justice. This harmony is best represented in the Sefirah of Tiferet, which exists midway between the extremes of Din and Hesed, female and male. Following traditional Rabbinic perception, the Kabbalah recognizes that the universe could not survive if it were founded only upon justice or only upon mercy.
You can learn about the individual Sefirot by clicking on their pictures in the diagram above or on the text below:
Sources: Prof. Eliezer Segal