There are many types of food mills on the market. A food mill is known as a "Passiermühle", a "Passe-vite" or "Flotte Lotte" in German. It is used for straining or pureeing fruits and vegetables, sometimes meats.
A "Flotte Lotte" consists of a sieve-like, convex plate which is placed in a hopper. A handle with a flat, corkscrew-head is fastened over that. The corkscrew-like head fits over the convex plate with just one edge touching and the two pieces form a "V" shape. The handle is hand-cranked horizontally over the machine, the "V"-shape catches the pieces of food placed in the hopper and forces them down, through the holes in the plate.
The "Flotte Lotte" is placed over a bowl to catch the fine particles of food. Any debris, skin or seeds which are too big or too hard to be forced through the plate can be discarded.
A food mill is usually used on cooked vegetables or fruit. If the fruit is naturally soft, it can be milled raw, as well. A common use for a food mill is to make potato puree. You can also use it to crush fruit for jams and jellies, applesauce or baby food.
In Germany, potato puree ("Kartoffelpuree") is distinct from mashed potatoes (Stampfkartoffeln) as a side dish. Potato puree is made perfectly smooth by forcing it through a food mill or ricer. Mashed potatoes are made by pounding cooked potatoes with a fork or potato masher. In this case, lumps are expected.
Another type of food mill is the potato ricer (See image). Cooked potatoes are placed in the hopper, then a solid stamp forces the potato through the holes (much like a garlic press). A potato ricer can be used with one hand, but a "Flotte Lotte" needs two hands to hold it steady and turn the crank.
A third type of food mill is used mostly in Scandinavian countries and is called a "Passierwiege" ("Passervagga" in Swedish), which translates approximately as a rocker-strainer (See image). A rectangular hopper with holes in the bottom and with feet, is used by placing food in it and pushing it through the holes with a stamper, a solid rectangle with a handle. The stamper usually fits precisely to the width of the hopper.
You may use a regular sieve and the back of a spoon for certain applications if you do not have a food mill. It is common to sieve tomato sauces and fruit purees for an extra smooth consistency.
The food mill was registered for patent on February 14th, 1928 by Victor Simon in Belgium. Jean Mantelet registered a similar patent on the 16th of February, 1931 and marketed it as Moulin-Légumes, which later became Moulinex.
The original "Flotte Lotte" in Germany has been produced by the GEFU company since the 1940s. Meanwhile, the brand name has become a common word for the machine (like Kleenex for tissues).
A bit of trivia: "Flotte Lotte" is also used to describe a speedy or industrious woman. "Flot" means quick and "Lotte" is a woman's name.