Cheese, said the ancient Greeks, was a gift of benevolent gods. Then, as now, cheese was a means of preserving milk, making it a useful, versatile food. Cheesemaking has evolved into an art practiced all around the world. There are hundreds of types available today, each with its own distinctive flavor and texture.

Many factors affect the flavor and texture of cheese, but the list can be simplified to include three main elements: the milk source, the cheesemaking process and the aging procedure.

Cheesemaking can be reduced to two absolutes: mammal's milk (whether cow, sheep, goat or buffalo's milk) and liquid extraction. Removing liquid matter (or whey) from the milk leaves semisolids (or curd) that contain protein, fat and nutritional value. Cheese is made from the curd. When milk sours, it naturally separates into curds and whey. To make cheese, however, the souring process is hastened in unspoiled milk by adding rennet (an enzyme found in the stomach lining of calves or other small animals) or lactic acid.

The size the curds are cut into determines the moisture in the final cheese. For soft, high-moisture cheeses, the curds are cut into large pieces. For hard cheeses, the curds are cut into small pieces or combed into strands.

To ripen, the cheese may be soaked in brine, waxed, washed, covered with ashes or left plain. Some cheeses are barely ripened, if at all. Popular unripened (or fresh) cheeses are cottage cheese, cream cheese and ricotta. Other cheeses may be aged for up to four years, during which time the cheesemaker manipulates and controls many conditions. For instance, holey cheeses are turned periodically to disperse holes evenly, and blue-veined cheeses are pierced with needles to add veins.

Natural cheeses are categorized by the amount of moisture they contain. Categories include hard cheese, such as Parmesan, with 30 percent moisture; firm, such as Cheddar, with 30 to 40 percent moisture; semisoft, such as Monterey Jack, with 40 to 50 percent moisture; soft and ripened, such as Brie, with 50 to 75 percent moisture; and soft and unripened, such as cream cheese, with 80 percent moisture.

Americans have access to an abundant array of cheeses, domestic and imported. Some of the most popular types are listed in the chart, Popular Cheeses in the United States (Cheese Chart in Index), although there are many others worth exploring.

Aside from the natural cheeses described above, there are other important cheese products, all made from natural cheeses.

Process cheese (or pasteurized process cheese) is made by grinding together different lots of cheese, some ripe, others "green." Water can be added along with chemical emulsifiers, and the mixture is heated. The advantage of process cheese is that it melts easily and smoothly.

Cheese food (or pasteurized process cheese food) is made much the same way as process cheese, but with added milk solids, moisture, salt and emulsifiers. It has more moisture than process cheese and shares similar melting characteristics.

Cheese spreads (or pasteurized process cheese spreads) are similar to process cheese and cheese food, except they are softer, more spreadable and often have added flavorings or ingredients, such as olives or garlic.

Coldpack cheese is made from several types of natural cheese that are combined into a spreadable product without heat or emulsifiers. This snacking cheese is often flavored or smoked.

Nonfat cheeses are made from skim milk. Special dietary needs may create a niche for them, but they may melt differently than other cheese products.

Cheese should be refrigerated. Unopened packaged cheese can be left in the original wrapping, but bulk cheese should be wrapped tightly in plastic wrap or foil. With the exception of cream-style cottage cheese, cheese can be frozen for two to three months; however, texture and taste will be affected to some degree. Cheese that has been frozen is best used in cooked dishes rather than for snacking.

A small amount of surface mold on hard or firm cheese can be cut away and the cheese safely used. With semisoft cheese, it is more difficult to judge the degree of mold penetration. If mold is limited to a small area on the surface, trim that part away as well as the surrounding area and use the rest immediately. Otherwise, semisoft cheese with several areas of mold should be discarded. Soft and fresh cheeses that show any sign of mold should be discarded.

Serve almost all types of cheese at or near room temperature for the best flavor. This is especially true of cheeses for appetizer and desserts where cheese is the star. Exceptions are soft, fresh cheeses, such as cottage and cream cheese, although even these are best when not too cold. However, cheese shreds or grates more easily when well chilled.

When cooking with cheese, use a low temperature and cook it slowly as high temperatures cause it to become rubbery. Cheese that is shredded or cut into very small pieces will melt quickly when added to hot liquid. Often the liquid mixture can be removed from the heat and the cheese stirred in.