Veal is the meat of a calf, generally from one to three months old. It's been considered a delicacy since Biblical times: when the prodigal son returned, they killed and ate the fatted calf.
Veal is prized for its pale tender fine-grained flesh and mild flavour. Colour is the main standard by which veal is judged: the best quality has creamy white flesh and white fat; if the meat is reddish, the calf was older when it was slaughtered and so is not, strictly speaking, veal.
Veal may be milk-fed, formula-fed, or "Bob" veal. Milk-fed veal comes from calves that have consumed their mother's milk; their flesh is firm and creamy white. Formula-fed calves consume a special diet of milk solids, fats, and vitamins, and is often sold as provimi veal ("protein vitamins milk"). This is considered the best quality veal because the flesh is very pale and soft, but it is bland and thin compared to milk-fed veal. Bob veal comes from very young calves, less than a month old; this is the by-product of the dairy industry: dairy cows are inseminated and give birth to calves that are removed right away, and the cows continue to produce milk.
In all cases, to keep the flesh of the calf pale in colour the animals are not allowed to eat grains or grasses, and their movements are severely restricted; in extreme cases they are held immobile in pens. Many people consider the treatment of veal calves inhumane and refuse to eat veal. This is fine, but you should be aware that chickens, cows and pigs are often fed similarly "unnatural" diets and have their movements severely curtailed in factory farm environments. gwenllian is concerned about hormones and antibiotics in veal, something else that is common to agribusiness; only organic and "naturally raised" meats will not have been subjected to these artificial additives.
Right then. Veal is usually sold fresh. The most common types of veal are very thin cuts from the shoulder - veal scaloppine (aka veal cutlets or wiener schnitzel) - and those from the ribs: rack of veal and veal chops. They need quick cooking; be careful not to overcook or they will be dry and tough. Veal bones and veal stewing meat are much prized by chefs for the excellent stock they produce, which is often reduced to make rich and delicious demi-glace sauce. Veal shanks are often crosscut and used to make osso buco; the meat and bones are rich in gelatine and so yield an unctuous sauce enhanced by the luscious marrow.