Nowadays everyone is obsessed with these specific names and ratios. Back then, coffee was just coffee. You add milk or you don't. Simple. But since you are asking for these new-fangled drink recipes, I will explain.
Everything starts with what they call "espresso". It's a very small, very strong coffee shot. Not much to drink on its own, in my opinion.
An Americano is when they take that small espresso and just add hot water to it. It basically makes a regular-sized black coffee, but more expensive. I don't see the point, just make a normal cup of coffee from the start.
Then you have the milky drinks. A Cappuccino is supposed to be one third espresso, one third hot milk, and one third of that airy foam. Very particular. A Latte is mostly milk, with one shot of espresso and then filled up with steamed milk, with just a little foam on top. It's basically a cup of hot milk with a hint of coffee flavour.
They are all just ways for cafes to complicate things and charge you more money for milk and water. The nutritional value is simple: coffee and water have none, so it all comes from how much milk they put in, which is alot.