Kether means the Crown. The Bible often talks about the Crown of Life. This is that Crown. This is the Father, Brahma.
The second one is Chokmah. This is the Hebrew word for Wisdom. In Sanskrit, this would be Vishnu, or Bodhi, for wisdom. This is the Sun, the Christ.
The third sphere is Binah, which usually is translated as Intelligence, or Understanding, but is directly related to perception. In Christianity this sphere is called the Holy Spirit.
These three spheres are the Tri-Kaya, the three bodies of the Buddha, which reside at the very root of our consciousness, but undeveloped. They are there in potential, but there nonetheless, for us to give birth. When our consciousness is fully developed, we then have elaborated our own Tree of Life, at the top of which are the three bodies of the Buddha, the three glorious bodies of the Soul. Immortality, perfect knowledge. Paramarthasattya, which means "perfect happiness, perfect truth, perfect knowledge." That is the ultimate potential that we have.
That doorway in the vertical path to ascend those levels is through the use of the consciousness now, in this very moment. Not by believing or thinking, but by using energy and matter wisely.
The three spheres at the top are the Trinity, the three-in-one, the three forces that are behind all of creation. So in the Book of Proverbs, we find a short passage which reads,
Happy is the man that finds wisdom (Hokmah) and the man that gets understanding (Binah).