He explained that there are many lights in the sky. Most of them stay put in the same places day after day. We call them stars. A very few of them don’t stay put, they constantly move about through the sky. We call them planets.
The planets move through a specific zone of stars. We call this zone the zodiac. We divide the zodiac in two main ways: in to 12 signs and 27 mansions.
There is one sign for each full moon that occurs during a normal year. Since there are 12 such full Moons, we have 12 signs. There is one mansion each day of the Moons cycle from full to new and back again. Since the moon takes just over 27 solar days to complete that cycle, we have 27 mansions.
There are 9 planets.
There are 12 houses. The sign that rises in the East becomes the First House, and the other eleven signs create the rest of the eleven houses in natural sequence.
The way the planets move within the signs, mansions and houses is the basis on which astrology can divine and predict the good and bad karma that will unfold at a given time and for a given person.