Subtext

Subtext is what is not said, but implied or suggested. It is something understood by the reader, watcher, or listener. of the work. 
Subtext suggests controversial subjects without being too obvious. This is especially true in comedy, but it is also common in science fiction. It can be easier and safer to make social critiques if it is set in another time and place.
Subtext is meaning hidden "under" ("sub") the actual dialog or text. To understand subtext the audience must "read between the lines" and infer meaning.