Better know an ingredient: RICE
The term rice refers to the seed of the plant Oryza sativa, native to Africa. Brown rice is rice that is harvested and has the hull removed. White rice is rice that has been harvested, has the hull removed and the bran is removed as well. The germ of the seed is also removed during this process, thus making white rice more shelf-stable since the fat source has been removed and it will not go rancid or sprout. White rice can be further processed by buffing (using talc or glucose, producing polished rice), or parboiling (producing quick-cooking, converted or minute rice).
Rice is often categorized by size: short-, medium- or long-grain.
-short-grain rice: the grains must be less than two times longer then the width.
-medium-grain rice: grains must be two to three times longer than the width
-long-grain rice: grains must be at lest three times longer than the width
In addition to the size of the grain itself, it these groupings also refer to the amount of starch released during the cooking process; the shorter the grain, the more starch is released, producing a creamier or sticker final cooked product.*
Long-grain examples: Basmati rice, Jasmine rice, Carolina rice, Himalayan red rice, Indian red rice, Kasmati rice, Thai black rice, Wheani rice, Surinam rice, Pecan rice, Texmati rice
Long-grain rices tend to hold their shape and easily fluff or separate after properly cooked.
Medium-grain examples: California medium grain rice, Southern medium grain rice, Black Japonica rice, Chinese black rice, Italian black rice, red rice, Valencia rice, Venus black rice
Medium-grain rices will release some starches and stick together when cooked. Some are used for risottos.
Short-grain examples: glutinous rice (does not contain gluten!), sticky rice, Arborio rice, Mochi rice, sushi rice, bamboo rice, Bhutanese red rice, Bomba rice, Carnaroli rice, Nishiki rice (used for sake production), pearl rice, Roma rice, sweet rice.
Short-grain rices are used when a creamy or sticky finished product is needed, like in the production of risotto or sushi. This category of rice is often ground into "sweet" or "Mochi" rice flour, used in the preparation of sweets and baked goods.
Wild rice is not technically “rice” because it is a seed of plant in the grass genus Zizania (What is commonly referred to as “rice” is Oryza sativa, which is in the grass family Poaceae.)
*It is more complicated than that. The wiki page on “rice” has links to the different types of sugars common in the different sized grains and their structures.