Teflon is a smooth, slippery plastic coating that food will not stick to. It is what makes a non-stick frying pan non-stick: the grey or black surface inside the pan is Teflon. You can fry an egg in almost no oil and it slides straight out.

Strictly it is a brand name, owned by a chemical company, so careful writers give it a capital T. But like Scotch tape or Google, it has slipped into ordinary speech as the everyday name for the material itself, and plenty of people write it small. If a pan says 'non-stick' rather than 'Teflon', that is usually a legal matter, not a different substance.

It is also a common word in kitchen warnings, because Teflon has a weakness: it scratches. Metal spoons and metal scrubbers take the coating off, and very high heat damages it. So you hear 'don't use a metal spatula on Teflon' constantly.

The interesting use is the one dictionaries often leave out. Because nothing sticks to it, English uses Teflon for a person — usually a politician — whom no scandal ever sticks to. Bad news comes out, everyone is angry, and a month later they are fine. 'The Teflon president', 'a Teflon politician', 'he's Teflon'. This is journalism and everyday talk, not formal writing, and it is nearly always a little sour: the speaker thinks the person ought to have been damaged and was not.