See below for screenshot.
Is there some system (stock) “section” widget where I can set the sub-widgets and the title, and Android will set up everything else (the fact title is in bold, with extra color in background) or this is custom made, like for example, by putting TextBoxes in navy, periodically, as logically section after section dictates?

These are subclasses of
PreferencesActivity, which provides those sub-headings.