The term “Vargas” refers to a category of charts that don’t break the zodiac up into 12 signs, but into multiples of 12 signs. Each varga has a unique number it multiplies with, and the names of most vargas are simply the name of that number.
For example, the Sanskrit word “Nava” means nine, and the Navamsha breaks the zodiac up into 9×12 signs. In other words, each sign of the zodiac is subdivided in 9 smaller parts, and these parts are considered as signs, following the same order Aries to Pisces.
The significance of the divisional charts is mostly derived from the house corresponding to the divisional number that is used.
However, Parashara does not prescribe vargas for every possible house number, and 8 of the vargas are divisions beyond the number 12. The reasoning of why these higher vargas indicate their respective areas of life is not explained in the classics.