When a planet is in the same sign in the birth chart and navamsa,then that planet is called Vargottama planet. It is coined from 2 words, Varga and Uttama. This is the best planet in the entire divisional chart.
There are other minor conditions which we can find Vargottama planets, but finding a planet in the same sign of D1 and D9 is the primary rule to find a Vargottama planet.
The idea is that the Vargottama planet will be very strong and it will help you with its own qualities. Or as a person, you will be displaying the qualities of your Vargottama planet. Your evident qualities will be the same qualities of your Vargottama planets. Different planet indicates different qualities. So, the nature of the Vargottama planet will change according to the planets.
Sun: The Sun indicates the soul, authority, will power, ego and self-esteem. So, if your Sun is Vargottama, then you will have a lot of will power. There will be a lot of intimations from your side. The Sun should not be in its debilitation sign Libra. Then the results can vary.
Moon: The Moon indicates the emotions, pleasure, nourishment, motherly love and happiness. When the Moon is the Vargottama planet, the qualities indicated by the Moon will be more evident in you. The Moon should not be in Scorpio, which is the debilitation point for Moon.
Mercury: The Mercury indicates communication, technology, media and intelligence. If your Mercury is well placed, then you will display a sharp intellect. Debilitation can be a problem and Mercury in Pisces generally means intellect is used for wrong deeds.
Venus: The Venus indicates love, luxury, comfort, money, strength and relationships. The Venusian qualities will be bright, if Venus is well placed. Venus is debilitated in Virgo, then that sensuousness of Venus will be hidden or unavailable.
Mars: The Mars indicates resistance, fighting spirit, valor, and vigor. Martian qualities are good when the Mars is Vargottama. If it is in cancer, then Martian qualities will need a lot of training to be under control. The wrong use of any skill can damage your social relations.
Jupiter: The Jupiter indicates wisdom, higher knowledge, higher studies, spirituality. Jupiterian qualities will be very much evident in your life. The Jupiter which is great benefic, and it should not be in the sign of Capricorn.
Saturn: The Saturn indicates delay, obstacles and stability. You may get a mind block when you find Saturn as your Vargottama. It is not to be feared, it just means you have stability and resistance to go through any bad event.
Rahu: The Rahu indicates rebelliousness, aggression, passion and mental disposition.
Ketu: The Ketu indicates isolation, detachment, spirituality.
You have to check whether your Vargottama planet is in a good placement in birth charts. If they are in 6th, 8th, and 12th houses, there can be variations in the results. These houses are known as negative houses or dustana houses. So, the qualities indicated by the planets can be at a different level and you have to really control that energy.
This Vargottama planet has to be in good aspects also. In any chart P( placement), A(aspect), C( Conjunction) is a valid matter. It will be ideal if they are with their good associates.
We have to check whether they are functional benefic or malefic as well. If the Vargottama planet is a functional malefic, then also variations in the results can come up.