Cream consists mainly of supernatant fat of skimmed milk.
In order to counteract this floating to the surface and keep the fat globules distributed in solution in the milk she is homogenized today : fat particles are evenly distributed. To this end, the milk is forced through small orifice under high pressure.

Milk from cows has a fat content of 3% (in winter, in the stable) to 6% (in summer, in the meadow). Whole milk is skimmed to 3.5%, semi-skimmed milk to 1.5% and skimmed milk to 0.5%.
Different cream types are usually classified according to their fat content, e.g. double cream: 45%, full cream : 35% (including cream), coffee cream : 15%, cream 20% fat (including sour cream). (Different countries use different terms and %’s.)

Cream tastes luxurious and soft and covers ​​ the taste buds and the food itself with a film. It is therefore used to correct (except salt and sweet) sharp or discordant flavors. Bitter soup, hot, too much mustard...
It is used in making or garnishing desserts and cakes, cream, whipped cream and ice cream, chocolate, special coffees, sauces, pasta dishes.

Whipped cream succeeds only with chilled cream (and tools!). By beating it the fat can hold air. If you beat too long you’ll get (irreversible) butter.
Creme fraiche (lightly natural soured cream) is made by acidifying pasteurized (whipped) cream by adding lactic acid bacteria to it. This thickens the cream.

You can also beat cream to whipped cream in a jar with some marbles by vigorously shaking it back and forth for a few minutes.

If you want to make butter, just shake a little longer.