You might already know the website GO INTO THE STORY by Scott Myers (if you don’t, please check it out, there is tons of useful stuff for aspiring and advanced screenwriters).
There are lots of different categories, and one I find especially interesting is called SCREENWRITING 101. Here is a quote from writer Carl Foreman (HIGH NOON) and it starts like this:
When I first came out to Hollywood, it never occurred to me that the story had to be about something.
Read the whole quote here, it is a pretty good definition of emotional theme. (Did I already tell you that I consider the emotional theme of a movie as important as three-dimensional characters?) You can find lots of other quotes here.