There are three culinary meanings of “to whip” in a kitchen.
To whip is to beat something with a utensil. The purpose is to incorporate air into it to provide body.
Usually it’s something liquidy being whipped that will hold air, such as heavy cream or eggs. Water for instance, is never “whipped”, as it wouldn’t hold enough air to make it worthwhile. The liquid to be whipped needs some “body” to it, usually fat, that can trap air.
Sometimes something non-liquid can be whipped as well, such as butter, if it is malleable enough to be whipped.
You don’t whip dry things such as flour, though.
The result of whipping is something that is fluffer than it was in its pre-whipped state.
Whipping is usually done these days with a whisk, with rotary beaters, or with electric beaters.
The act of whipping eggs is also referred to as beating.
The Tool Called a “Whip”
A whip as a utensil is something like a whisk, but with only a few lines of wire looped and attached to a handle. See Whisks entry for more information.
To produce something quickly
The word “whip” is colloquially used in the sense of “producing something quickly and effortlessly.” As in, to “whip up dinner” or “any cook should be able to whip up a pasta sauce in no time.”
Pasteurized eggs take about four times as long to reach a soft-peak stage through whipping as do non-pasteurized eggs.
See the entry on Whipping Cream for tips and facts on whipping heavy cream.