What does it mean by update requested?

Your iPhone sends a "request" for the update software to be downloaded from a server over the Internet back to your phone.

Whether or not the server on the other end actually receives the request and responds is open to question.

If things go correctly, the update software is downloaded back to your phone so the software update can continue right at the phone.

If things don't go well, you have to start over again with the update process.