The fact is that sometimes Kabbalah speaks from the Light’s point of view, and sometimes from the Kli’s. We shouldn’t forget that this duality is always present. We never talk about the Light separately from the desire, or about the desire separately from the Light. We talk about the desire which feels the Light as it changes form. The desire calls these forms, “Light.”
One form relative to another is called the Light against the Kli. The Kli of the Upper One in relation to the Kli of the lower one is considered the Light. We are talking about qualities that are relative to one another. The Upper One is one that bestows more, and is therefore called Light relative to the lower one. The lower one is the one that receives more and is therefore called the vessel or Kli.
We are accustomed to vessels that are metallic or glass and which are filled with something. But in spirituality this is completely not the case. The quality of bestowal, which exists inside the vessel, is called Light. The quality of reception is the Kli. But all of this exists as qualities of the desire. We are always talking about the desire alone, and about its ascents and descents. Its higher forms are called Light, and its lower forms are called Kli. Therefore the Creator (Boreh) is called Bo-Reh (come and see), because we see Him inside our own Kli. The form of bestowal that is imprinted inside the Kli is called Light, the Creator.
These are very important concepts because they correct us in the right direction, in order for us to cross the veil and enter the spiritual world by learning to relate to our desires correctly. They are all just different forms of reception and bestowal.