Zenith and Nadir
Imagine looking directly up into the heavens from the location on the Earth where you were born, from your "natal location." This point in the heavens is called your "Zenith." Imagine standing on that location, but that your body extends through the Earth such that you feet extend through the opposite side of the Earth. That point projected into the heavens is called your "Nadir." Your Zenith and Nadir are always opposite each other in the heavens, just as are Earth's north and south celestial poles. The Zenith-Nadir axis creates your personal pole. You can think of it as the energy running through your spinal column.
The stars and constellations surrounding your Zenith reveal much about how you are guided in your life, your soul-level focus. The Nadir stars and constellations reveal much about your soul-level foundation.