The material in the right-hand text pane, which is the $Text field of a note, is just stuff I have entered. It could be cut and paste, it could be interview notes, it could be anything. It's just material I may want to refer to when I'm writing.
I do the actual writing in Scrivener. These TB files are strictly research notes for me. When I want to see what I have on a certain theme (or by a certain author or about a certain city), I go to this page and check out the notes..
$Theme is a User Attribute, one of several that suit my personal research / info-organizing needs. Others you see on this screen are $Chapter, which refers to where I want to use it in a book; $CityName, which is the city it refers to; $Used, which is whether I have already quoted it etc. $Used is a Boolean attribute. The rest are set-type attributes. If you're unfamiliar with that, Mark A tells you more here.