Prix fix is French for “fixed price” and refers to a set amount you pay for a dinner with many courses. You pay the same whether you get the escargot or saltines as an appetizer.
Some restaurants feature prix fixe menus every day, while others offer them only on holidays, like New Year’s Eve. Any time you see a menu listing a full meal with very few (if any) choices, all for one price, you can call it prix fixe. This French phrase has been used in North America since the late nineteenth century. You can also call this a table d'hôte menu, or less exotically, a set meal or set menu.