Indian classical music identifies 12 major notes out of 22 as Swar. It is quite interesting to study the names given to each of these Swars::

1. Sa: Shadja

2. Re: Rushabha

3. Ga: Gandhara

4. Ma: Madhyama

5. Pa: Panchama

6. Dha: Daivata

7. Ni: Nishadha

Together, they form: Sa Re Ga Ma Pa Da Ni

There are two types of Swar: 1. Achal and 2. Chal. Chal literally means movement or motion and achal means fixed or static. 

Achal Swar: In Indian Classical Music, the two notes: Sa and Pa are fixed- static. They don’t have any major or minor notations- their shruthi sthaans or positions are fixed. These two notes Sa and Pa are therefore called Achal Swar.

Chal Swar: These are the ones that have multiple fixed notes under a single note. In a sense, they are all static and fixed but each note is composed of a bunch of notes making it a dynamic range of static notes. Re, Ga, Ma, Dha, and Ni are Chal Swar. 

Chal Swar are classified into 3 forms: 

1.  Shudh (pure): All Chal Swar Re, Ga, Ma, Dha, Ni 

2. Komal (tender or soft): Re, Ga, Dha, Ni 

3. Teevr (intense): Ma

Counting the 5 shudh swar, 4 komal swar and 1 teevr swar- there are 10 Chal Swars.

So adding 2 Achal Swar + 10 Chal Swars, we get 12 Swars.

Sa Re Re Ga Ga Ma Ma  Pa Dha Dha Ni Ni