India is a country where you will find people of various religion. However the majority are Hindus, Sikhs, Christians, Muslims etc.  
Following are a little details about some of them:

Hinduism

Hinduism is the name given to a family of religions and cultures that began and still flourish in India.

Like other Eastern religions, it doesn't fit comfortably into the same box as Western religions like Christianity.

Hindus do not separate religion from other aspects of life. For Hindus in India, Hinduism is an inextricable part of their existence, a complete approach to life that involves social class, earning a living, family, politics, diet, etc., in addition to the things Westerners view as religious.

The word "Hindu" comes from the name of the river Indus, which flows 1800 miles from Tibet through Kashmir and Pakistan to the sea. Originally the name referred to people living in a particular region of the world, regardless of their faith; so in the 18th century someone could quite sensibly be described as a "Hindu Muslim".
There are 750 million Hindus in the world, and most of them live in India. In the UK there are 400,000 Hindus, 160,000 of whom are active in their faith.

Hinduism includes a very wide range of beliefs and practices, so there aren't many things that are common to all Hindu groups. However they all have a "family resemblance" to each other.

Hinduism has no founder, no creed, and no single source of authority.

The things most often common to Hindus are a belief in a single Divinity or supreme God that is present in everything, belief in other gods who are aspects of that supreme God, belief that the soul repeatedly goes through a cycle of being born into a body, dying, and rebirth, belief in Karma, a force that determines the quality of each life, depending on how well one behaved in a past life.

Most Hindus worship at home and have a shrine there. Hindu temples are the focus of religious life, but there is not a strong tradition of corporate congregational worship.

Hinduism has not had a significant tradition of seeking to convert people, although some modern Hindu sects now do seek converts.

Sikhism

Sikhism is the youngest of the world's four great monotheistic religions. It was founded in the 15th Century by Guru Nanak.

The view that Sikhism is a variety of Hinduism is completely wrong, and gives great offence to Sikhs.

There are 18-20 million Sikhs in the world, and 80% of them live in the Punjab state in Northwest India, where the faith began.

There are 500,000 Sikhs in Britain, 80% of whom are active in their faith. 39% of UK Sikhs attend a religious service at a Gurdwara (temple) once a week.

Other countries with large Sikh communities are Canada (225,000) and the USA (100,000).

The word "Sikh" is Punjabi for "disciple" and Sikhs are disciples of the Gurus.

Sikh men are particularly easy to identify because they all have a full beard, and wear their hair uncut and contained in a turban.

The Sikh place of worship is called a Gurdwara or temple.

Sikhism does not have priests, but most gurdwaras will have a Granthi. A Granthi is a learned Sikh who is skilled in reading the scriptures, however, a Granthi has no special religious status.

The principle Sikh scripture is the Adi Granth, often called the Guru Granth Sahib.

Sikhs believe that the words of these scriptures are the present day embodiment of the Sikh Guru and they treat the book with the respect and devotion that they would have given to a human Guru.

Sikhism does not actively look for converts, but it is thoroughly welcoming to those who do want to convert.

Christianity

Christianity is a religion practised by nearly 2,000 million people worldwide.

It originated in Palestine in the 1st century AD and is founded on the life and teachings of Jesus Christ [4BC-29AD], a Palestinian Jew.

There are 6 million active Christians in the UK, but over 35 million in Britain would regard themselves as nominally Christian.

There are many different variations or "denominations". The major division is between Orthodox and Western Christianity (which itself is divided into Roman Catholicism and Protestantism).

From the beginning, Christianity has sought to convert people, however, many Christians today feel there should still be respect for what is good and true in other cultures and religions.

Islam

Islam is the world's second most followed religion.

It began in its present form 1400 years ago in Arabia, but swiftly become a world faith, and now has around 1,200 million adherents.

There are between 1.2 and 2.6 million Muslims in the UK, about 600,000 of whom are active in the faith. Those who are not active still regard being a Muslim as an important part of their identity.

"Islam" is an Arabic word which means surrendering oneself to the will of God, and achieving peace and security by doing so.

A person surrenders to the will of Allah by living and thinking in the way Allah has instructed.

Islam is more than a system of belief. The faith provides a social and legal system and governs things like family life, law and order, ethics, dress, and cleanliness, as well as religious ritual and observance.
The countries with the largest Islamic populations are in Asia rather than the Middle-East.

These are Indonesia (170 million), Pakistan (136 million), Bangladesh (105 million), and India (103 million).

However, Islam's two holiest places, the cities of Mecca and Medina, are both in Saudi Arabia.

Buddhism 

Buddhism is a vast and complex religious and philosophical tradition which stretches back over 2,500 years.

Over the last 30 years Buddhism has seen growth in the West as its non-dogmatic nature, rationality, possibility of a spiritual guide, and opportunity for personal transformation have all made it attractive to post-modern society.

It has about 500 million adherents around the world-45,000 active Buddhists in UK

'Buddha' means 'one who has woken up'. Most people live asleep, never knowing or seeing life as it really is. As a consequence they suffer. A buddha is someone who awakens to the knowledge of the world as it truly is and so finds release from suffering.

A Buddha teaches out of sympathy and compassion for the suffering of beings and for the benefit and welfare of all beings.

Buddhism does not actively look for converts, but it is thoroughly welcoming to those who do want to convert. Buddhism can coexist with other faiths.

Judaism 

Judaism is the oldest of the world's four great monotheistic religions. It's also the smallest, with only about 12 million followers around the world.

The Holocaust of the 1930s and and 40s transformed Jewish demographics-if the Holocaust had not occurred there would now be between 25 and 35 million Jews in the world, and far more of them would live in Europe.

Most Jewish people in the world live in Israel or the USA. The largest European Jewish community is in France.

There are 285,000 Jews living in the UK. Only 85,000 of them are active in their faith, but virtually all the others still regard being Jewish as a vital part of their identity.

Judaism does not seek converts. Those who convert to Judaism must undertake the observance of Torah (Jewish Law), including, if they are men, circumcision.