What does func FileServer() do in this example (DotFileHiding)?

Question

go

Explain what the code in this example does - https://golang.org/pkg/net/http/#FileServer , Example (DotFileHiding) ?
What are the magic dots in the name (string/URL)? What happens to them in the end? And why in the end such a strange http.Dir(".")?
Does the URL get modified there before getting to FileServer()? Or is the directory of the server files specified in FileServer() being modified?