Liz asks via Twitter:
Not a question asked directly to me, but a good question nevertheless, so I figured it was worth looking into. After all, there are quite a few things that aren't quite cheese available for purchase in the American grocery system, and one wonders if it's really food or if it's some kind of specialized plastic that's meant to stand in for food.
Regular cheese is generally made by heating up some milk, adding some acid and possibly some rennet, and letting coagulate. You then drain off all of the stuff that isn't coagulating, let cool, and age the cheese. Sometimes you want microorganisms to feast on the cheese to give it some extra color and flavor, and sometimes you don't. Sometimes you'll put some ash into the cheese, sometimes you don't. There are a lot of variations, but the general idea is: thicken the milk, let it coagulate, drain, and possibly age.
American cheese is done partially this way. American cheese is a blend of several cheeses, especially colby and cheddar. In its natural state, it is white, but you often find coloring agents have been added to it to make it orange. Some other products are added to the cheese, for the purpose of getting a specific texture, melting point, and the like. For details on the chemistry of American cheese and related products, I recommend "What's that stuff? - Process Cheese from Steve Ritter at Chemical and Engineering News of the American Chemical Society. It covers the differences between "cheese food", "cheese spread", "cheese product", and "imitation cheese". Mind you, his view on these things are that they're beneficial to our society, and I don't particularly share that view.
The thing about all of those almost-cheeses is that they they are made with a purpose, and that purpose is almost never "to have a lot of good and unique flavor." More often than not, the goal is to make something that is mild in flavor so as not to offend picky children, and to have specific textures and melting properties that you don't get out of a proper cheese.
Textures are important to various processed cheese products because it's really difficult to squirt real cheese out of a can. Even your softer cheeses don't react well enough to pressure to squirt faithfully onto a cracker just because you press a button, and because good cheese is often still alive, you'll find that the texture might change as it ages and is under different conditions.
Melting properties are important when you want to have a cheesy sauce but you don't want to go through the trouble of mixing some flour with butter, then combining that mixture with milk on the stovetop until you have a thickened sauce you can add the cheese into. So instead you take the entire block of thing-that-contains-some-cheese and you melt it until you have a cheese sauce, suitable for dipping vegetables into or mixing with noodles.
I do love cheese, and I am a bit fan of engineering and science, but frankly I hate the flavor of all of the processed cheeselets. I would rather take a blend of cheeses that I choose and mix them together for something that has character and flavor rather than have something that is inoffensive to the majority of people who buy processed food. Reach for something fantastic, don't settle for something easy.
The thing about cheese is that, while it's great stuff, you probably don't want to eat it all the time, nor do you want to eat it in great quantities on most of your more healthful foodstuffs. If you like cheeseoid foods then I'm glad your life is easier, but you might be well served by limiting the amount of cheesish stuff that you put on your foods. The nice thing about taking the time and effort to make a sauce mornay is that, though it's incredibly tasty, you don't really want to do it every day. But opening a jar, putting it into the microwave, and pouring the result on to a batch of steam-in-a-bag broccoli is hardly work at all, so you'll be tempted to do something like that on a regular basis. You should resist that temptation.
There are a lot of cheeses out there, and there are new and interesting varieties being made every day. If you like real cheese, please take time time out to try those rather than the things that aren't legally allowed to call themselves cheese. Personally, I think you'll have a better and more interesting life for it.