In western terms 'flour' without further qualification usually means wheat flour.
Flours are defined by whether they contain bran and germ or not, by their colour and by the type of grains milled to make them. Wholemeal, is a brown wheat flour that contains the whole of the grain. White flour is milled only from the starchy endosperm of the grain, with none of the bran and germ.
Flour can be plain or self-raising (with raising agents added to it), or can be strong (sometimes labelled 'bread' flour) if it is milled from a hard variety of wheat that is high in gluten. Granary which is made from a mixture of wheatmeal flour and malted wheatflakes, and Hovis, white wheat flour mixed with cooked wheatgerm, are both proprietary brands of flour.
Baking is a major use for flour, and different types are recommended for different forms of baking. Strong flour is preferred for yeast baking since it contains more gluten-forming proteins than soft wheat flours - it is the gluten that makes yeast doughs elastic and helps bread to rise.
Plain and self-raising flours are better for cakes and biscuits, where the aim is for a light, crumbly texture, and for most pastries. Flour is a major ingredient is other dishes too, such as dumplings, pasta and batters for pancakes, Yorkshire puddings and so on. It is also used to thicken sauces, gravies and stews, and as a coating for fish fillets, chicken joints and meats that are to be fried.