yield return www - What is www referring to?

In the instruction:

yield return www;

which method is being called in the WWW class of the www variable?

It’s not calling a method - its waiting for the object to say that its done and then continuing.

something like:

     yield return null;

you are waiting for something to download, wait for it to complete then return the www object.

Documentation of WWW class.

Quote from the documentation:

Simple access to web pages.

This is a small utility module for
retrieving the contents of URLs.

You start a download in the background
by calling WWW(url) which returns a
new WWW object.