Please define for me the following locations in Italy in terms of
whether it is a town, district or region etc. and how if at all they
relate to each other: Castel di Sasso, Prea, Caserta, Piedemonte
Matese, in Italy. By "relate to each other" I mean if one is a town in
the district of --- in the region of ----.

Dear marjo,

"Prea" is a small town. It belongs to the Commune of "Castel di
Sasso", which is part of the Italian Province of "Caserta", in the
Region "Campania".

"Piedimonte Matese" is another Commune in the same Province. You might
want to have a look at their official website:
http://web.tiscali.it/matese/

Additionally, this is the website of the Province of Caserta:
http://www.provincia.caserta.it/

Note: An Italian Commune consists of several towns and villages.

Source:

Province of Caserta: Communi della Provincia di Caserta
http://www.campania.org/enti/regionali/comuni_prov_caserta.htm

Search terms used:
"castel di sasso"
://www.google.de/search?hl=de&ie=ISO-8859-1&q=%22castel+di+sasso%22&meta=
caserta
://www.google.de/search?hl=de&ie=ISO-8859-1&q=caserta&meta=

Hope this answers your question!
Best regards,
Scriptor