Usually, the word "flour" used alone refers to wheat flour, which is one of the most important foods in European and American culture. The corresponding Spanish word "harina" normally refers to Maize flour - wheat flour is "harina de trigo".

Wheat flour is the main ingredient in most types of breads and pastries. Wheat is so widely used because of an important property: when wheat flour is mixed with water, a complex protein called gluten develops. The gluten development is what gives wheat dough an elastic structure that allows it to be worked in a variety of ways, and which allows the retention of gas bubbles in an intact structure, resulting in a sponge-like texture to the final product. This is highly desired for breads, cakes and other baked products. However, certain individuals suffer from an intolerance to wheat gluten known as coeliac or celiac disease. Increased awareness of this disorder, as well as a rising belief in the benefits of a gluten-free diet for persons suffering certain other conditions, has led to an increased demand for bread and other products made with flours which do not contain gluten.

Wheat varieties are typically known as, variously, "white" or "brown" if they have high gluten content, and "soft" or "weak flour" if gluten content is low. Hard flour, or "bread" flour, is high in gluten and so forms a certain toughness that holds its shape well once baked. Soft flour is comparatively low in gluten and so results in a finer texture. Soft flour is usually divided into cake flour, which is the lowest in gluten, and pastry flour, which has slightly more gluten than cake flour.

Milling of flour is accomplished by grinding grain between stones or steel wheels. Today, "stone-ground" usually means that the grain has been ground in a water-operated mill, in which a revolving stone wheel turns over a stationary stone wheel, with the grain in between. Many small appliance mills are now available, both hand-cranked and electric.

In history, both large and hand mills were operated. Until modern times, much flour contained minute amounts of grit, either the result of poor sifting of the grain or of grinding stones together. This grit strongly abraded teeth.

One of the most ancient methods of grinding to produce flour was by using a pair of quern-stones. These were made out of rock, and were ground together by hand. They were generally replaced by millstones once mechanised forms of milling appeared, particularly the water mill and the windmill, although animals were also used to operate the millstones.

Bread, pasta, crackers, many cakes, amongst many other foods, are made using flour. Wheat flour is also used to make a roux as a base for gravy and sauces. White wheat flour is the traditional base for wallpaper paste. It is also the base for papier-mâché. Cornstarch is a principal ingredient of many puddings.