It is a philosophy. Carl sagan had to say this about it:

Hindu religion is the only one of the world’s great faiths dedicated to the idea that the cosmos itself undergoes an immense, indeed an infinite number of deaths and rebirths. It is the only religion in which the time scales correspond, no doubt, by accident, to those of modern scientific cosmology. Its cycles run from our ordinary day and night to a day and night of Brahma 8.64 billion years long. Longer than the age of the earth or the sun and about half of the time since the big bang. And there are much longer time scales still. There is the deep and the appealing notion that the universe is but the dream of the god who after a 100 Brahma years… dissolves himself into a dreamless sleep… and the universe dissolves with him… until after another Brahma century… he starts… recomposes himself and begins again the dream… the great cosmic lotus dream.

"When we think of the Hindu religion, unlike other religions in the world, the Hindu religion does not claim any one prophet; it does not worship any one god; it does not subscribe to any one dogma; it does not believe in any one philosophic concept; it does not follow any one set of religious rituals; it does not satisfy the narrow traditional features of any religion or creed.** It may broadly be described as way of life and nothing more." ** --Indian chief justice.