Indian Classical Music, a long musical tradition from the Vedic period, having its own theory, and grammar is completely based on the theory which is called Shastra. That's why this subcontinental music is called the Shastriya Sangeet.
Bhartiya Shashtriya Sangeet, actually the Indan classical music is the best in compiled music from generation to generation with the systematic formation of pitch and scale in various melodic structures. It is structured with strict grammatical rules and regulations and principles of Raga and the melodies but it has wide space to elaborate the musical fragrance with its fame. It has no imprisonment beyond its principle and grammar and each and every artist can explore their own innovations and creativity to explore the Journey of melodies through Raga in Bhartiya Shastrya Sangeet restricting the melody within the nomes and frame of the Raga. It has a boundary but having no limits to explore the musical essence, fragrance, and beauty of sound and the microtonal elaboration through the moods of every individual artist. It depends upon the creativity: practice and innovation of artists that how much he/she can explore the musical core through Raga with fundamental theories.
There are two major classifications in Indian Classical Music supposed to divide in the 13th Century after the Mughal invasion in the Northern part of the Indian subcontinent. The foreign rulers attack Bharat Desh from its western corner and move towards to eastern and northern parts and ruled over the centuries. Persian, Arabian, Turkish empires, and the Sultanates of Mughals whose arrival in Bharat with different cultural and linguist behavior mixed with the Hindu tradition, results from the mixture which eventually named as Hindustani Shastrya Sangeet and Carnatic Music. The northern and North Western part of India was mostly captured by the Mughals so the fertility of Classical Music tradition was mixed with the Persian music and Arabic influence in their court were as the southern part of the Indian subcontinent was less influenced by the Sultans and Mughals so the pure tradition of Vedic Music remain unchanged in South India.