is a combination of the 格助詞（かくじょし） (case marking particle) と, and the う - Verb 言（い）う. It is a set expression that primarily uses only hiragana. という
connects two nouns, and means ‘the (B) that is called (A)’, or ‘the (B) known as (A)’.
Do you know the model called Rola?
Please get off at a station named Motoyama.
If you find a child named Tanaka Tarou, please call us.
(and the verb 言（い）う itself) is often quite misunderstood, as the closest translation in English is ‘to say’. In Japanese, 言（い）う actually refers to the information about something that cannot be discovered by simply ‘looking at’ it. For example, if you look at a man, you cannot know that his name is Bob, or that he works in an office, but you can know whether he is ‘short’, ‘tall’, etc. Due to this, という
should only be used to express information that requires intimate knowledge, and not simple observations.
Did a man called Bob come here?
Did a man known as small come here?
It is possible to see (A) という
(B) in sentences where (A) is describing something that seems ‘obvious’. However, in these cases, the speaker is usually implying that something about (A) is not exactly as it seems, or that their opinion/knowledge differs.
That person is known as strong, but don't you think he uses steroids? (He looks strong, but isn’t)
This particular nuance is not limited to nouns, and may be seen with almost any word type.