Cheddar, often sold as "American" or store cheese, constitutes about two-thirds of the cheese sold in the United States.
If you don't have a refrigerator, there's no way to keep milk from going bad within a few hours, especially if you live in a hot climate like Africa or Western Asia. Even WITH a refrigerator milk goes bad in about a week. But ancient cows and sheep and goats only gave milk part of the year, right after they had had their babies in the spring. By mid-summer their milk had all dried up. How could people manage to preserve this milk to be able to eat it in the fall and winter as well?
They made it into cheese. The easiest kind of cheese to make is yogurt, which was very common in the ancient Mediterranean diet and in India (and still is today). If you leave milk out on the kitchen counter on a warm day, it will soon get all lumpy and turn into a kind of yogurt. This is because bacteria get into the milk from the air and turn it into yogurt. Some of these kinds of bacteria are bad for you, or make the milk taste bad. But if you get the right kind of bacteria in your milk, it turns into good yogurt. Yogurt tastes good, and it will keep for a few days without being refrigerated, but it still won't keep all winter.
Once people realized how to make yogurt, they began experimenting with other types of bacteria, and found that you can use different bacteria to make aged cheeses. Some of these cheeses can be kept without being refrigerated for four or five years or even more. Swiss cheese is an example of an aged cheese that you might have eaten. Or cheddar cheese.