<Text like this signifies actual spoken word. Anything in this text is meant to be representative of the real world, i.e. the world that is actually factual. This sort of speech is often (but often not) understood by the "main characters" Piro and Largo, and is usually ignored/not understood by them. Unlike popular belief, this does not represent actual Japanese or whatever.>
All other speech like this is the figment of Piro's imagination. In general, this is why Japan seems so exaggerated and Anime-like- it's all generally a construct of both his mind and that around him. He seems generally conscious of the "outside" world (except the <> stuff above), but still seems to become confused, which is when this speech is used more.