That's a great question. One thing you always want, is to work on items that are super-small, but still valuable in their own right. That also means that a Sprint Backlog should contain many small items, rather than just one or two large ones. It's all about flow; large items don't flow well.

The Sprint Goal was the overarching purpose of the Sprint, which we used to select the small items to make up the Sprint Backlog. Or to break-down larger items into smaller ones.

Does that help?