Vargottama means “the best place in the set” – where “the set” is talking about the amsha divisions, specifically in this case about the most important amsha, the navamsha. The “best place” is to be in the same sign in the navamsha as the planet is in in the normal zodiac – you got that correct.
As to what it actually does for planets… “gives a planet extra special strength.” Consider it like this… if I am in new york, I have certain resources at my disposal. Now, if I am in New York CITY within the state of New York – I am “really” deeply in New York, and those resources are very ample. That is what it is like for a planet to be in vargottama. The planet has very deep, full and ample access to the resources specific to whatever sign the planet is in.
– Vic DiCara
Vic DiCara's Astrology 
Hi Vic Ji,
Same sign right and not house? For example in my lagna venus is in 12 house which is dhanus. And in my Navsamsha Venus is in 12th House but which is cancer.
-Praveen SA
LikeLike
Vargas are divisions of the stars, divisions of the signs. They are not divisions of the sky, the houses. Therefore you are correct. Vargottama does not pertain to being in the same house in both the radix and the navamsha.
LikeLike
If the planet is weak or malefic, the vargottama condition increases or alleviates the effect? is the difference between strong condition and good condition in our past conversations
LikeLike
why try to fit everything into an “increase” / “cancel” black and white paradigm? Such thinking does not allow access to the inner working of astrology. I have described what Vargottama is and does in summary. You have to sincerely apply your intelligence, rational and intuitional, applied consistantly over a prolonged period of practice to figure out details in application.
LikeLike