Wiktionary
n. A mixture of bay leaf, parsley, sage, rosemary and thyme
Wikipedia
Herbes de Provence is a mixture of dried herbs typical of the Provence region of southeast France. Formerly simply a descriptive term, commercial blends started to be sold under this name in the 1970s. These mixtures typically contain savory, marjoram, rosemary, thyme, oregano, and other herbs. In the North American market, lavender leaves are also typically included, though lavender does not appear in the recipes in Jean-Baptiste Reboul's 1910 compendium of Provençal cooking.
As the name herbes de Provence is generic, and not a Protected Geographical Status, there is no guarantee that any herb mixture on the market actually comes from Provence; indeed, the vast majority of these blends come from central and eastern Europe, North Africa, and China.
Herbes de Provence are used to flavour grilled foods such as fish and meat, as well as vegetable stews. The mixture can be added to foods before or during cooking or mixed with cooking oil prior to cooking so as to infuse the flavour into the cooked food. They are rarely added after cooking is complete.
Herbes de Provence are often sold in larger bags than other herbs, and the price in Provence is considerably lower than for other herbs.
Provençal cuisine has traditionally used many herbs, which were often characterized collectively as herbes de Provence, but not in specific combinations, and not sold as a mixture:
...the famous mixtures of herbes de Provence... were unknown to my Provençal grandmothers, who used, individually and with discernment, thyme, rosemary and savory gathered in the countryside.
It was in the 1970s that homogenised mixtures were formulated by spice wholesalers, including notably Ducros in France (now part of McCormick & Company).