Dosha means some Defective Aspects of life.. Only Malific Planets (Papa Graha) creates dosham. Some of the doshas are said to be Kuja Dosha, Sarpa Dosha, Pithru Dosha, Sthree Dosha and Puthra Dosha.
Kuja dosha is quarrels. Sarpa dosha is the deviation from their culture, Pithru dosha is difficulties due to the parental karmas. Sthree dosha is no happiness between husband and wife sometimes separation. Puthra Dosha means no issue or children will give troubles.
It is a vast subject and nowadays people with little knowledge try to fix the matching of their own. They give in matrimonial columns like the boy has kuja dosha and only girls with kuja dosha need to apply. These are absurd.
There are different impacts of various doshas. For example kuja in 2nd house, 4th house, 8th house and 12th house are not equal. But people believe that if a girl has kuja dosha, the same should be there in boy’s horoscope also. Kuja in 8th may indicate physical risk of the partner. Kuja in 4th will not find peace at home. How can we equate both.
The impact of dosha is to be studied by an expert astrologer. The question is when the said dosha will affect. If it is immediately after marriage it will break the life. If it affects after the age of sixty we won’t give importance to the dosha.