Very amusing video
Gmail is incredibly powerful, but it hides some of the more common features of e-mail under the surface. For instance, you can see at a glance that you have n unread messages, but how to actually see just those messages isn’t immediately obvious.
In the search field, type
in: inbox label: unread
and you will see only the unread messages that are in your inbox. If you want to search in all folders, omit the in: label.