These are words which are especialy important, within the context of the section. These are to help see words that the author lists embedded in sentences. In long sentences with a lot of pronouns, it can be difficult to trace the pronoun back to what it is referring to. This is used to highlight the pronoun as well as well as what it means. This is used to highlight when the author makes a summary or conclusion statement based on the text above it.
Some words have multiple meanings, depending on the time the text was written or translated.