The seven sur or 'swara' are 'Sa, Ri.Ga,ma,Pa
Dh and Ni.
They are each a base sound staring from base and ascending. A music learner firs has to 'fix' the basic sound or swarasthana. This is reinforced by basic instruments like harmonium. After many repetitions under the guidance of a teacher, the student can reproduce the corresponding to each sur or swara correctly , even when woken up from sleep.
The Ragas or the tune in which a song is sung is actually a permutation and combination of these swaras. A raga contains generally a combination of five swaras.
Such basics are also there in Western system of music. The notation symbols are mostly for western system. In the Indian system it is written as the letter of the surs.
Based on the combinations of sur, there are some basic ragas. Apart from these, a creative composer can make many variations also.
For easy description these swaras, are named with the first letter -example Rishabam for Ri, Nishadam for Ni , Madhyamam for Ma etc.
Whetehr to sound hard or soft or melodious is termed with qualifying words like Komal Nishad etc.