Cream is made by separating milk into fat-rich cream and an almost fat-free (skimmed) milk. This is usually done by centrifugal force.
There are many varieties of cream, categorized according to the amount of milk fat in it:
Light cream, also called coffee or table cream, can contain anywhere from 18 to 30 percent fat, but commonly contains 20 percent. It can not be whipped.
Whipping cream contains 30 to 36 percent milk fat and sometimes stabilizers and emulsifiers. Whipping cream will double in volume when whipped.
Heavy cream, also called heavy whipping cream, is whipping cream with a milk fat content of between 36 and 40 percent. It's usually only available in specialty or gourmet markets.
Half-and-half is a mixture of equal parts milk and cream, and is 10 to 12 percent milk fat, and can not be whipped.
All cream, unless ultrapasteurized (briefly heated to 149°C/300°F and then cooled), is highly perishable and should be kept in the coldest part of the refrigerator.
Whipped cream in pressurized cans is a mixture of cream, sugar, stabilizers, emulsifiers and gas, such as nitrous oxide. It is expanded by the gas into a "puffy" form. Aerosol "dessert toppings," which are usually made with hydrogenated vegetable oils, have absolutely no cream in them (and doesn't taste like cream either).