Rice is without argument the most important food source on this planet, and apart form China, the largest consumption of rice takes place in that other 1 billion - plus populace, India. Most people immediately think of basmati rice when considering Indian cuisine, yet most of that population rarely tastes this noble rice.
Basmati is the most highly revered rice in India; some would argue the world, prized for its amazing non-stick abilities and subtle yet beguiling aroma. To assume that the general Indian populace ate basmati rice each day would be akin to saying that westerners dined on caviar with the same regularity. While basmati is reserved for wealthy citizens and religious festivals alone, patna rice is the work-horse - the daily bread as it were for countless millions of Sub-Continental residents.
Just like basmati, and most other rice varieties on the planet, patna rice belongs to a single and amazingly diverse species, Oryza sativa. Patna rice, along with many of the 200 varieties of rice grown in India, takes its name form the region where it is grown. It is closely related to basmati, and thus shares many of its characteristics - its long grains, while opaque, unlike basmati's translucence, still cook to a fluffy and separately grained dish. It does not share the same enchantingly subtle aroma as basmati, but cannot be ignored for what it is - the most important food source for the second most populous country on the planet.
Rice has long been associated with religious and cultural significance. There is even a leftover tradition in western cultures that showers newly-weds with the grains. Rice has an exponentially greater cultural significance in India, beginning with weddings, and moving onto more poignant occasions, such as Navanna Purnima, the first full moon after autumn when the rice harvest begins. This is considered the night of "new food"; when the last years harvest is appreciated and next years is begged to be better. During Navanna Purnima, candles and lanterns are lit after dusk has fallen and the freshly harvested and un-husked rice is offered to Hindu Gods.
Patna rice presents a similar physical shape to basmati rice - it belongs in the indica group of rices - that is long-grained and separate after cooking, but patna has more rounded edges to its length, opposed to basmati's severe tapering.
This rice is fairly hard, and because it is plentiful and cheap, it is often used for milling into rice flours used in Indian battered dishes such as bhaji. The fabulous dosa, or Southern Indian pancakes of rice and lentil most often uses patna as its base.
Patna rice can be hard to find outside of India. Because Western countries are so much wealthier, there seems little need to export rice that would be considered everyday in its home country. Yet patna has its adherents, and not only with expatriate Indians. In a truly bizarre display of cultural and economic revision, patna can be found in the west, but only at specialist Indian grocers and at a higher price than basmati rice.
As with all long grain rices, I would suggest the absorption method of cooking. Anthropod has beaten me to the prize, so use her faithful and true-to-tradition method, which is noded here.