Nirvana is everywhere, at least for English speakers. The word has been adopted into English to mean "bliss" or "tranquility." Nirvana is the name of a famous American grunge band, as well as of many consumer products from bottled water to perfume. Nirvana also appears to be a popular name for Asian-themed restaurants. But what is it, really? And how does it fit into Buddhism?
In the spiritual sense, nirvana (or nibbana in Pali) is an ancient Sanskrit word that means something like "to extinguish," with the connotation of extinguishing a flame. This more literal meaning has caused many westerners to assume that the goal of Buddhism is to obliterate oneself. But that's not at all what Buddhism, or nirvana, is about.
Liberation, Not Obliteration
The ancients considered fire to be an element, one of the most basic forms matter could take. In the culture of India at the time of the Buddha, fire was thought to be equivalent to air, or something like aether (but not exactly).
It was understood that we can see fire as flames only when fire is stuck to some kind of fuel. When fire is trapped by fuel it becomes hot and agitated, and flames are visible. When the fire is separated from fuel it passes into a different state. Although the fire is no longer visible to humans, it still permeates existence, coolly and serenely.
That is not at all how we understand fire today, of course. However, this understanding does explain why the Buddha used the word nirvana to mean "liberation" or "unbinding."
So nirvana is liberation, but liberation from what? The standard answer is "samsara," which usually is defined as the cycle of birth, death, and rebirth. (Note that "rebirth" is not necessarily reincarnation as you might understand it.) Nirvana is also said to be liberation from dukkha,or the stress/pain/dissatisfaction of life.
In his first sermon after his enlightenment, the Buddha preached the Four Noble Truths. Very basically, the Truths explain why life stresses and disappoints us, and why we are stuck and struggling like a flame stuck to fuel. The Buddha also gave us the remedy, and the path to liberation, which is the Eightfold Path.
Buddhism, then, is not so much a belief system as it is a practice that enables us to stop sticking ad struggling.
Nirvana Is Not a Place
So, once we're liberated, what happens next? The various schools of Buddhism understand nirvana in different ways, but they generally agree that nirvana is not a place. It is more like a state of existence. However, the Buddha also said that anything we might say or imagine about nirvana will be wrong, because it is utterly different from our ordinary existence. For this reason,it also defies definition, because language is inadequate to define it. Nirvana is beyond space, time, and definition.
Many scriptures and commentaries speak of entering nirvana, but (strictly speaking), nirvana cannot be entered in the same way we enter a room, or the way we might imagine entering heaven. The Theravadin scholar Thanissaro Bhikkhu said, "... neither samsara nor nirvana is a place. Samsara is a process of creating places, even whole worlds, (this is called becoming) and then wandering through them (this is called birth). Nirvana is the end of this process."
We do sometimes get stuck using words like "enter," however, because English vocabulary hasn't developed words that properly relate to nirvana.
Of course, many generations of Buddhist have imagined nirvana to be a place, because they couldn't imagine it as not a place. So you may run into Buddhists with that understanding. There is also an old folk belief that one must be reborn as a man to enter nirvana. The historical Buddha never said any such thing, but the folk belief came to be reflected in some of the Mahayana sutras. This notion was very emphatically rejected in the Vimalakirti Sutra, however.
Nibbana in Theravada Buddhism
Theravada Buddhism describes two kinds of nirvana -- or nibbana, as Theravadins usually use the Pali word. The first is "nibbana with remainders." This is compared to the embers that remain warm after flames have been extinguished, and it describes a living enlightened being, or arahant. The arahant is still conscious of pleasure and pain, but he or she is no longer bound to them.
The second type is parinibbana, which is final or complete nibbana that is "entered" at death. Now the embers are cool. The Buddha taught that this state is neither existence -- because that which can be said to exist is limited in time and space -- nor non-existence.
Nirvana in Mahayana Buddhism
One of the distinguishing characteristics of Mahayana Buddhism is the bodhisattva vow. Mahayana Buddhists vow to remain in the phenomenal world and strive to bring all beings to enlightenment. This is not done just a in sense of altruism, but with the understanding that it cannot be otherwise. In at least some schools of Mahayana, because everything inter-exists,"individual" nirvana is nonsensical.
Mahayana Buddhism also teachings that samsara and nirvana are not really separate. A being who has realized or perceived the emptiness of phenomena will realize that nirvana and samsara are not opposites, but instead completely pervade each other.