Hinduism is the most popular religion in India.
I guess everyone (somehow) heard about Hinduism, even without knowing it; yoga, karma, reincarnation etc., all come from Hinduism.
I have the (wrong!) impression, that Hinduism is the religion of everyone from India. Actually, less than 20% of the population are Islam followers. Taking into account the total population of India, this 20% is quite a large number!
There are also smaller numbers of other religions followers.
What’s interesting – the Constitution of India has declared freedom of religion as a fundamental right.