Ketu Puja is suggested to remove the malefic effects of Ketu Graha. The Ketu Puja bestow a person courage and confidence to get rid of illness. It heals negative position of Ketu in person's horoscope.
Ketu Puja is done to please the ruling Graha/ planet and to earn its sympathy so he (Ketu) can function as a supporter rather than persecutor or dictator. Ketu is believed to indicate the wrong deeds or the bad karma of previous birth and their outcomes as hardships in present life. When Ketu is at 2nd, 4th, 5th or 7th house in a person's horoscope it will bring negative influences in life such as arrogance, over confidence, lazyness, imaginative, frustration and depression. People with negative ketu will always look shortcut in life due to their imaginary world. Later it realise that the path choosen by them practically doesn't exist in real world.
According to the Hindus Mythology Ketu is regarded as a Shadow Graha (Planet) or Chaya Graha. It is also one of the Navgraha which has an important role in Astrology. It is unique in many aspects. It doesn't have any physical appearance or own any figure or sign in the Nature's Zodiac. Yet it gives immense effects in human life. The Ketu Graha is a wicked/ vicious planet still it has a spritual aspect and also non attachment towards worldly affairs. It makes KAAL SARP DOSHA with Rahu, which brings many unwanted incidents in life i.e. accident, sudden loss, legal cases, health issues, loss of property and wealth. Though it is a part of Navgraha, still it's actually a Headless Half Garha or a tail of Snake whose Upper Part or Head is "RAHU", his equivalent Graha. His colour is Brown.
Ketu is a Gyana Karta or the Knowledge Giver as it make human go through with difficult times and learn from those bad experiences. He gives real/ practical first hand experiences of life. As per human general belief Ketu is not assumed a s a giver but he is a great saviour or rescuer. Ketu signify electronics, maternal ancestors, religious beliefs, super natural/ paranormal activities, healing art and practices and Superstitions.
Ketu is basically considered as a malefic planet who control pain suffering and anguish of a person. According to ketu position in person's horoscope, it can give favourable and unfavorable impact in life.