Supermarket.

While looking around the supermarket I noticed the section of canned foods. Since corn is yellow, the can caught my eye. There were many different types of canned corns. There was sweet corn, white corn, fiesta corn, whole kernel corn. What's the difference? Is a specific type any better or worse? I also noticed that there were many different brands of corn. The Associated brand canned corn was .75 cents, Del Monte brand was $1.25, Green Giant was $1.29, and Libby's was $1.35. Why is the Associated brand so cheap? Is it because it was produced differently? How much better/worse is it for your health? Can canned foods actually be good for you? Since the corn is mass produced, is the corn they use less healthy then corn that is sold as regular corn (not in a can)? I didn't look at the expiration dates but canned foods can obviously be saved for much longer than fresh corn, so how long does it last before going bad? All of this made me a little bit grossed out about eating canned foods, I don't know how long they have been on the shelf or where/how the corn was produced.
I also saw all of the different milks. There is soy milk, organic milk, fat free milk, 2%, lactose free (how is that possible?), 1%, half and half, chocolate milk, whole milk. Some of the milk was not in the refrigerator, it was on a regular shelf. I know that in France, you don't have to keep your milk in the refrigerator until it's opened but I don't really get it. Doesn't milk have to be kept fresh? What exactly is soy milk? I know that cows milk does not taste the way that milk from a carton tastes, how many different things do they add to the milk to make it taste that way?