Mangal Dosha
Mangal Dosha is an astrological combination that occurs if Mars is in the 1st,2nd, 4th, 7th, 8th, or 12th house of the Vedic astrology Ascendant chart. A person born in the presence of this condition is termed a manglik.
This condition is astrologically believed to be devastating for marriages, causing discomfort and tension in relationship, leading to severe disharmony among the spouses and eventually to other bigger problems. This is attributed to the "fiery" nature of this planet. However, if a manglik person is born on Tuesday, the negative effects of Kuja Dosha gets cancelled by itself. Also, if two mangliks marry, the negative effects are believed to cancel each other out. However, Mars is not the only planet in Vedic Astrology that is supposed to affect the relationship and these effects should be seen in a broader perspective of overall astrological compatibility.
There is also a belief that the negative consequences for a single-manglik marriage can be resolved if the manglik first performs a ceremony called a kumbh vivah, in which the manglik "marries" a banana tree, a peepal tree, or a silver or golden idol (Murti) of the Hindu God Vishnu. Before her marriage to Abhishek Bachchan, Aishwarya Rai one of India's most famous film stars faced a lawsuit, after being accused of entering into a "false marriage" ('marrying' a tree) by Lawyers on behalf of some human rights groups.[1]
Any person suffering from Manglik Dosh is called a Manglik. So when someone says "I'm a Manglik", it simply means that they have Manglik Dosh in their horoscope.
The bad effects of Manglik Dosh can be reduced with the help of astrological remedies which would generally include the application of Pooja, Mantras, Gemstones and Charities and these remedies are different for different individuals depending upon their horoscopes.
An increasing number of individuals are placing less emphasis on Manglik dosha, during the selection of a life partner, as evidenced from the data from online matrimony sites. However, there is still a pretty large following of people who give credence to Manglik Dosha.