Flour (farina term from the Latin, which in turn comes from far and farris, farro old name) is the fine powder is obtained from ground grain and other starchy foods. You can get different cereal flour. Although the most common is wheat flour (cereal from Asia, habitual element in making bread), rye flour, barley, oats, corn (grain from the Americas) and rice (cereal is also made from Asia).
There flours legumes (chickpeas, beans) and even in Australia flours made from seeds of various species of acacia (acacia flour).
The common denominator of vegetable flour is starch, a complex carbohydrate.