The House System
Astrologers use the system of 12 houses to interpret different aspects of our life and which house heavily determines of path in life. Houses are generally numbered counterclockwise from the Ascendant, with the house which begins at the Ascendant being called "The first house".
The dividing line between one house and another is referred to as a House Cusp. An example: when the Sun moves from the 10th house into the 9th house at 12 noon, it is crossing the 10th house cusp. The most powerful house cusps are the 1st, 4th, 7th, and 10th. The various house systems differ only in by means of techniques in calculation. There is a long list of them, the most commonly known are Campanus, Porphyry, Koch, and Placidus.
Understanding the house system is not as straight forward as changing from one sign into another. Planets which occupy there positions at the end of a house are often interpreted as in the following house.