The horizontal line you are talking about is actually a punctuation mark called proper name, which is used to indicate names such as names of people, places, dynasties, races, countries and institutions. What you see in the book are basically names and places, which are convenient for readers to read and will not be confused.
Small print is a comment, which may be the pronunciation of some words, the time of the event, the deeds of people and so on. And it is a further explanation of some words and sentences in an article or a book.