It is meant to be a short summary of the project. Kind of similar you
get from the first sentence of function/class/etc description.
Just title is not quite sufficient. Just look at JavaDoc for JDK -
you've got title "Java(tm) Platform, Standard Edition 6", you've got
summary "This document is the API specification for version 6 of the
Java(tm) Platform, Standard Edition." and long description down below.