Wheelbarrows carry more goods from place to place using less force than a person could carry them. In fact, a person would have to make several trips to carry the items by hand. With the help of the wheelbarrow's two simple machines---the lever and the wheel and axle---people can save time during the process of hauling.I think there might be more to mention in the way of ergonomics, and in traditional details that create more functionality than is at first apparent.
All over the internet is "wheelbarrows were invented by the Chinese," but I don't think it's valid. Their "wheelbarrow" (what English speakers called a wheelbarrow) is a whole different thing, and though it can do some things European wheelbarrows can't, theirs can't do some of what is quite normal for our little short-distance, imperfect wheelbarrows.
Thinking of what ours are used for might give some ideas for what I'm thinking of in way of features gathered and improved over hundreds of years.