Before we dive into that, let's dispense with a technicality: Teflon was DuPont's original brand name for what now goes by various unattractive pseudonyms, such as "non-stick coated aluminum cookware," as well as a poetic variety of brand names. I'll call these slippery coatings "non-sticks."
In the early days, what the non-stick stuck to was a mechanical issue.
Manufacturers textured a pan by blasting its surface with grit, gouging little pits in the aluminum, or by spraying the cookware with a micro-lumpy ceramic coating or stainless steel, which formed mini-mountains as it hardened. These textures gave the long, slippery non-stick molecules much more to brace themselves against. And when the non-stick wore off the peaks of the mini-mountains and micro-lumps there was still enough clinging to the slopes and valleys to keep the flapjacks flipping. Trouble was these methods didn't hold up very well under normal household use, leading to a chorus of feminine voices across America, singing out in harmony, "touch that fork to that pan and you are a dead man."
The bottom line was that the non-stick didn't stick to the pan long enough. The basic non-stick molecule is a polymer, or chain, of fluorine atoms and additives such as carbon and hydrogen. The longer this chain, the tougher it is; but a molecule that's too long gets viscous and hard to handle. To move beyond mere mechanics, the frying-pan engineers added a sticky molecule to the non-stick molecule. Non-stick was now applied in coats, with the bottom coat containing the sticky additive that held to both the metal pan and the non-stick molecules. A coat of non-sticky non-stick went over that, non-stick and non-stick clinging together lovingly. A final non-stick layer, spiked with teensy bits of ceramic or other tougheners, protected the softer guts. This is...