How has trade affected us today?

Trade in general means that you don't have to do everything yourself. You can do one or two things, and when you need something, you trade what you have for what you want.

At its simplest level, that's all "trade" is. I have an Apple tree; you have a cow. I can offer Apples, and get milk or cheese in return. To smooth out the times when I have too much of one thing, we can trade my Apples for tokens that represent value that I can use for other things later. We call these trading tokens "money".

I teach computer classes (really) and I like to eat steak. Some people who need to know how to use a computer program give me money, and I spend this money at the grocery store. The grocery store doesn't have cows of their own; they buy the beef from the meatpacking plant and give them money for beef. The meatpacking plant uses the money to buy steers and cows from the farmer. The farmer raises the cows and steers, and gets money from them. The farmer uses the money for all the stuff HE needs, including trips to Disneyland or - wait for it! - computer training for his children.