What are Rahu and Ketu?

Rahu is the north node of the moon. It is not a physical planet but only  a virtual astronomical point. Nevertheless it is very significant in astrology. It has a malefic  nature and it will magnify the other existing features in a person's horoscope. It indicates materialism, greed, worldliness , drugs, liquor, gambling and other bad qualities. It can  cause extreme feelings such as  covetousness, lust and never ending greed for money, material benefits and worldly fame. In rare cases when it is afflicted by other malefic planets it can also cause neurosis, psychosis, suicidal tendencies and other mental problems. On the positive side rahu can  give huge amount of money, power and prestige. Generally successful politicians will have a strong rahu in their charts. Rahu will also create hallucinations, unrealistic imaginations and extreme desire for money and enjoyment in life. Generally rahu will cause harm but it's harmful effect can be mitigated by the influence of powerful benefic planets such as jupiter. 

Ketu is the south node of the moon. It is not a physical planet but only a virtual astronomical point. It also has a malefic nature like rahu and it will cause chaos and financial loss depending on it's position in the horoscope. It has a tendency to magnify the existing factors in the horoscope and cause some big event which may be good or bad depending on the nature of the ruling planet of the house in which ketu is placed in the horoscope. On the positive side it can give wisdom, deep intuition, spiritual knowledge, mastery of esoteric subjects and psychic sensitivity.  Ketu is a karmic planet which indicates one's deeds in past lives. Ketu also signifies liberation or moksha or separation from worldly things and in that sense it is not favorable for materialistic success in this world. Generally people with prominent rahu or ketu linked to their ascendant will have a mean, deceitful, unreasonable and greedy nature. Both rahu and ketu will give boldness, success and victory in competitions if they are placed in the third, sixth, tenth or eleventh house in the birth chart.