Skimming means to remove a small amount of something from the surface.
In cooking, it usually refers to removing fat from the surface. That’s if you don’t just whisk it back in quickly, before the Health Police see. In any event, if you have a plastic bulb baster, you can use that, or the edge of a big spoon to gather it up and scoop it up. The best way to skim, whether skimming fat or say coagulated film on the top of milk, is to hold a paper towel by one edge, and drag it across the surface of the liquid to be skimmed. The paper towel will soak up what’s on the surface. You can do a couple passes, if you need to, with the same piece. This will save you loads of time and get up just what it is you want to be skimmed off.
When skimming is used to refer to money, it’s illegal, unless of course it’s the government doing it to your paycheques, in which case it becomes legal again. But then, that’s less skimming and more scooping, isn’t it?