Reactive pans are made of metal, period. That is, the cooking surface is metal. With the exception of gold, and titanium, all metals corrode. on steel and iron, its called rust. On alluminum, and copper, it's called oxidation. The point is that oxidation is caused by the ability of oxigen to combine with other elements. Acidic and base/alkalie ingredients (citric & ascorbic acids, strong cheeses, buttermixk, yogurt, etc, & baking soda for a base) encourage electron flow between these chemicals and oxegen, changing the base metal to an oxidized metal. In turn, some of the metal molecules are turned into free ions (unstable mollecules with either too many or to little electrons), that attach themselves to foods, and liquids, given them a an unwanted metalic flavor.
There are many factors that cause corrosion, dissimilar metals and an electrolyte such as walt water, the afore-mentioned acids and alkalies, heat, and reactive gasses. But for the purpose of cooking, bare metal reacts with food PH levels.
Plastic or ceramic coated metals (teflon, enamled cast-iron), glass, and stainless steel are inert. They don't react with acidic or alkalie foods. (Stainless steel is really stain-resistant steel. It will rust if abused sufficently.)
The reason we use metals is that they are malleable (can be bent and formed into the shapes we want), are good heat contuctors, and are durable. They also conduct electricity well (important if you own and induction stove as it is the eddy currents created by interaction between the metal and an electro-magnetic field generated by the stove "burners" that cause the metal to heat). Glass, ceramic, and plastic, as a rule, are insulators to heat and electricity, though there are exceptions. But they are not perfect insulators and so can absorb and retain heat, espcially the glas and ceramics. And once they are hot, they have substantial thermal mass and retain heat well. That is, as they transfer heat to the food, there is lots more stored in the material.
The problem with both glass and ceramics is that they are extremely rigid materials and will shatter due to expansion and shrinkage pressures caused by rapid temperature change (hot glass placed in cold ater).
This can also be a problem with cast iron, though it can withstand subtantially more drastic temerature changes than can glas and ceramic vessels.
The problem with plastics is that they degrade rapidly at any temperatures past 400 degrees. That is, they start to outgas and deteriorate. They are not good for hight-temperature cooking.
So there's a quick and not very scientific synopsis of the nature of various cooking vessels. Take this info, think about what you want the cooking vessel to do to the food, and what you want to use it for. After that, all becomes second nature.
And remember, there are other variables involved. A well seasoned piece of cast iron has a coating of something akin to carbon, that is not reactive, and encases the metal in a hard, slippery shell that is much like teflon in performance, except that you can't hurt it with high temperatures. But it can be scraped and washed away with strong emulsifying and alkalye agents such as good dish-soaps, especially automatic dishwasher soaps. (it is an oil-bases coating). With sufficient elbow greese, it can also be removed with steel wool, or other metalic cleaning pads.
Know and take care of your pans and they will take care of you.
Oh, and the least durable pans are pans coated with non-stick finishes, followed by ceramic coated (enamled) pans.
Seeeeeeeya; Goodweed of the North
