The concept of astrology is based on the movement of the earth and surrounding planets. The center of the universe being the SUN. The position of SUN signifies the human soul, the MOON signifies the human mind and the position of EARTH which means the ascendant or "LAGNA" this signifies the HUMAN BODY. It is the combination of the three i.e. the MIND, BODY and SOUL that makes a perfect human being.
The whole UNIVERSE is divided into 12 parts each one being 30 degrees, hence the total circumference of the earth is 360 degrees (12 signs into 30 degrees each). The rising sign at a certain longitude determines the descendent or "LAGNA". There are a total of 27 Constellations and each constellation has 4 PADAS" and thus in total 27 X 4 = 108
"PADAS". It is the position of the MOON viz. the placement of moon in any nakshatra determines the MAHADASHA (MAIN PLANETARY RULE) at the time of BIRTH.
The Explanation about the 12 signs are as follows :-
The first house is called TAN BHAO the physical body and various other factors.
The second DHAN BHAO the accumulation of wealth.
The third being PARAKRAMA BHAO "VALOUR".
The fourth SUKH BHAO viz. place of residence, peace of mind etc.
The fifth being Progeny and the sub-concious mind.
The sixth being related to disease, enemies and death.
The seventh is related to life partner, business partner etc.
The eighth is related to hidden parts of the body and cause of death.
The ninth being DHARAM or BHAGYA BHAO.
The tenth being Professional , Carrier etc.
The eleventh is related to fulfillment of desire and financial gains.
The twelveth being the last house deals with expenditure for good and for bad
( Broadly called VYAYA BHAO relating to spending your physical energy also)