India has a very rich tradition of folk music. The extreme cultural diversity creates endless varieties of folk styles. Each region has its own particular style.

There is a tendency to lump folk music along with tribal music. There is actually a difference. Where folk music is a mere rustic reflection of the larger Indian society, tribal music often represents cultures that are very different. Some of these tribal cultures are throwbacks to cultural conditions as they were thousands of years ago.

Tribal and folk music is not taught in the same way that Indian classical music is taught. There is no formal period of apprenticeship where the student is able to devote their entire life to learning the music, the economics of rural life does not permit this sort of thing. The musical practitioners must still attend to their normal duties of hunting, agriculture or whatever their chosen profession is.

Music in the villages is learned almost by osmosis. From childhood the music is heard and imbibed along with ones mother's milk. There are numerous public activities that allow the villagers to practice and hone their skills. These are the normal functions which syncronize village life with the universe.

The music is an indispensable component of functions such as weddings, engagements, and births. There is a plethora of songs for such occasions. There are also many songs associated with planting and harvesting. In these activities the villagers routinely sing of their hopes, fears and aspirations.

Folk music is also used for educational purposes.
Listed below are a few styles:
Bauls

The Bauls of Bengal were a gay order of musicians in 18th, 19th and early 20th century India who played a form of music using a khamak, ektara and dotara. The word Baul comes from Sanskrit batul meaning divinely inspired insanity. They are a group of mystic minstrels. They are thought to have been influenced greatly by the Hindu tantric sect of the Kartabhajas as well as by Sufi sects. Bauls travel in search of the internal ideal, Maner Manush (Man of the Heart).

Bhangra

Bhangra is a lively form of music and dance that originated in the Punjab region. As many Bhangra lyrics reflect the long and often tumultuous history of the Punjab, knowledge of Punjabi history offers important insights into the meaning of the music. While Bhangra began as a part of harvest festival celebrations, it eventually became a part of such diverse occasions as weddings and New Year celebrations. Moreover, during the last thirty years, Bhangra has enjoyed a surge in popularity worldwide, both in traditional form and as a fusion with genres such as hip-hop, house, and reggae, and in such forms it has become a pop sensation in the United Kingdom and North America.

Bhavageete

Bhavageete (literally 'devotional song') is a form of expressionist poetry and light music. Some notable Bhavageete performers include P. Kalinga Rao, Mysore Ananthaswamy, C. Aswath, Shimoga Subbanna, Archana Udupa, and Raju Ananthaswamy.

Dandiya

Dandiya is a form of dance-oriented folk music that has also been adapted for pop music. The present musical style is derived from the traditional musical accompaniment to the folk dance.

Lavani

Lavani comes from the word Lavanya which means beauty. This is one of the most popular forms of dance and music that is practiced all over Maharashtra. It has in fact become a necessary part of the Maharashtrian folk dance performances. Traditionally, the songs are sung by female artistes, but male artistes may occasionally sing Lavanis. The dance format associated with Lavani is known as Tamasha. Lavani is a combination of traditional song and dance, which particulary performed to the enchanting beats of 'Dholak', an drum like instrument. Dance performed by attractive women wearing nine-yard saris. They are sung in a quick tempo. The verve, the enthusiasm, the rhythm and above all the very beat of India finds an expressive declaration amidst the folk music of India, which has somewhat, redefined the term "bliss". Lavani originated in the arid region of Maharashtra and Madhya Pradesh.

Pandavani

Pandavani, literally means stories or songs of Pandavas, the legendary brothers of Mahabharat, and involves the lead singer, enacting and singing with an ektara or a tambura (stringed musical instrument), decorated with small bells and peacock feathers in one hand and sometimes kartal (a pair of cymbals) on another. The origins of this singing style are not known, and according to its foremost singer Teejan Bai, it might be as old as the Mahabharata itself, as few people could read in those times, and that is how perhaps they passed on their stories, generation after generation.

Rabindra Sangeet

Rabindranath Tagore was a towering figure in Indian music. Writing in Bengali, he created a library of over 2,000 songs now known by Bengalis as 'rabindra sangeet' whose form is primarily influenced by Hindustani classical, sub-classicals, Karnatic, western, bauls, bhatiyali and different folk songs of India. Many singers in West Bengal, and Bangladesh base their entire careers on the singing of Tagore musical masterpieces. The national anthem of India and national song of Bangladesh are Rabindra Sangeets

Rajasthani folk music

Rajasthan has a very diverse cultural collection of musician castes, including Langas, Sapera, Bhopa, Jogi and Manganiyar. Rajasthan Diary quotes it as a soulful, full-throated music with Harmonious diversity. The haunting melody of Rajasthan evokes from a variety of delightfully primitive looking instruments. The stringed variety include the Sarangi, Rawanhattha, Kamayacha, Morsing and Ektara. Percussion instruments come in all shapes and sizes from the huge Nagaras and Dhols to the tiny Damrus. The Daf and Chang are a big favourite of Holi (the festival of colours) revellers. Flutes and bagpipers come in local flavours such as Shehnai, Poongi, Algoza, Tarpi, Been and Bankia.
The essence of Rajasthani music is derived from the creative symphony of string instruments, percussion instruments and wind instruments accompanied by melodious renditions of folk singers.

Source: Wikipedia and chandrakanta.com