Tohu is the secret of the first Tzimtzum that is when the Endless removed himself from a middle point to create ‘space’ for the creation of the four worlds.
During the phase of Creation that is called Tohu, there was no definition of vessels. The ten Sefirot were in a potential state without light.
Bohu is the secret of the ‘curtain’,’מסך’ (pronounced ‘Masach’) that was created to separate between Light and the vessel after the first Tzimtzum. The Light of the Endless then continued into the Sefirot of Atziluth and the lower worlds.
Malchut can’t receive direct light but able to reveal the returning light as Light of Chassadim.
Zohar Beresheet is hard to understand without knowledge of the Tree of Life. I will publish soon studies (videos and charts) to explain the entire process from Endless light before Creation, forming the Sefirot, create the worlds and the process of Creation, to the world we live in.
Keep a closer look for when these studies are posted on the website. They will come in addition to the Daily Zohar studies. Don’t miss any of them because one builds on the previous one.