The stickiness of Japanese rice---the way the individual grains cling together----is due to its high proportion of starch. Starch is itself composed of amylose and amylopectin. Their proportions can vary according to the variety of rice, but in general if the level of amylose is low and amylopectin is high, you get sticky rice---the kind of rice grown in Japan. The other chief characteristic of Japanese rice's stickiness is the soft but noticeable bounce it delivers. There are many Japanese dishes, like sushi, that take advantage of this stickiness. The grains of Indica rice as longer, narrower, and don't hold together as well when cooked. You could say that the very stickiness of Japanese rice had enabled Japanese cuisine to become what it is.
Rice that is sold all over the world to make dishes like rice pudding tends to come in several varieties. Among these are varieties that are sticky like Japanese rice, including Japonica rice grown elsewhere and Javonica rice, whose grains are larger than Japonica rice.
Our Japanese rice paper, washi, is made with traditional Japanese craftsmanship, but the material is not actually rice. It is typically made from the pulp of mulberry or mitsumata trees. Perhaps because in other countries, paper is made with various grasses that resemble rice, people might make the same assumption and call washi "rice paper."
To best prepare Japanese rice to taste good as part of a meal, it's important to rub off any dirt or rice bran that might be attached to the surface of the grain. The rice absolutely needs to be washed before being prepared. Actually, the verb people have long used to describe this action is not "wash," but something more like "sharpen" or "hone." As the grains of rice are rustled together in water, because the rice bran that sticks to the surface is rubbed off, the rice grains have that function. These days, it's more usual to get already polished rice, so the rather vigorous effort required of unpolished rice is not necessary. It's fine just to wash it in a quick minute or two (without soap, of course). Recently, a pre-washed rice called musen-mai is being marketed.
Rice is a sort of dried food. Part of the knack of cooking it well is to make sure that the water is infused into the very middle of each grain during the cooking process. Please cover the rice with water and let it soak before cooking it. Ideally, soak it for about 30 minutes in summer and an hour in winter.
After cooking, separate it into small portions while it is still hot. The best way to save it is to wrap it in plastic wrap and freeze it. That way you can thaw out only the amount you need or heat it up using a microwave and it will retain its taste. The freezer life of the rice is about a month. But the best way to eat the best-tasting rice is to only cook as much as you need, and to finish it all at one sitting.