Introduction to Kabbalah: Who is God and How Do I Find Him/Her/It?

The Infinite Being is boundless and without beginning. Except for this Infinite Being, everything else that exists has a beginning. At first there arose in Him the potential to emanate from His own essence all the worlds that existed potentially within Him. When the will of the Infinite Being decided to create, He brought existence from potential to actuality. First the Infinite Being emanated its sefirot, through which its actions are performed. In this way all worlds were brought into being; indeed, all that exists came into being from Him, from the depths of the earth to the loftiest heavens.
This Infinite Being, known as Ein Sof, fills all the worlds of time and space. Both the heavens above and the earth below are equally filled with His light. There is no place empty of Him in the upper or the lower worlds.
Howard Schwartz, Tree of Souls, p. 9

What are the Sefirot?
The Sefirot – God emanates ten vessels through which the world is created, called sefirot, which are both part of God and created by God. These vessels are channels of light or water, and they also are light. They are God and of God, but they cannot define God or limit God – what is truly God is wholly beyond these descriptions, beyond the first sefirah, called Keter or crown, denoted by the term Ein Sof – without limit, without end.
When Kabbalists read stories in the Torah, every character and place represents a configuration of the Sefirot. For example, the binding of Isaac is Chesed (Abraham) overcoming Gevurah (Isaac). A (secular) technical term for how the Sefirot function is that they are "hypostases" (sing. "hypostasis") – that is, abstract concepts imagined as beings or as parts of a reality that are more real than the physical world around us ...
The Structure of the Sefirot – for the Zohar, an essential aspect of this world is that the Sefirot are emanated in the form of a Mishkal or balance scale, with a center, right and left, which can be pictured as the form of a triangle or triad. This allowed each Sefirah to share the force of creation with those around it, so that none would shatter because of the influx of God's energy. Each of the Sefirot also contains within itself an element of all the others. (Sarah Idit Schneider's term for this is that they are "interincluded" within each other.) This fractal structure is one way in which the Sefirot are infinite or divine in their essence.
Rabbi David Seidenberg, neohasid.org/kabbalah/sefirot/

Tzorekh Gavoha or "high need", the meaning of the mitsvot – Mitsvot or commandments fulfill a tzorekh gavoha – a high need – meaning, a need on high, a need within God or the cosmos on the level of the Sefirot. The commandments have a cosmic impact of bringing blessing, while sins can bring cosmic tragedy. For example, according to one interpretation, during the week there is a wall of fire between Shekhinah (or Malkhut – kingdom, the cosmic feminine) and the Holy One (or Tif'eret, the masculine), but on Shabbat the fire goes out so that they can unite. We don't light fire on Shabbat in order to help this happen. This was a radical rejection of Jewish (and Christian and Muslim) rationalist philosophy. Philosophy had taught that God has no need whatsoever (this was a lemma [assumption] to the concept of God's perfection), and that any idea to the contrary was heretical to monotheism.
Rabbi David Seidenberg, neohasid.org/kabbalah/themes/