Used to specify or define one noun with another; 'the noun called', 'the noun that is' or 'a certain'.
Long explanation:
The Noun という Noun construction is used to specify or define one noun with another. It usually translates as 'the noun called', 'the noun that is' or simply 'a certain'. It is a common grammatical pattern in Japanese, where a noun is clarified or specified by another noun.