The byline on a post gives the name of the writer. It might also display some other post data like publication date, categories and comments count. Whether and where it is displayed depends on your theme.
Themes normally make author name on bylines link to that author’s archive page (learn more about author archives). That’s standard behavior so everyone expects it to work like that. However, Molongui Authorship allows you to disable that feature to prevent author names to be a link.
Molongui Authorship Pro extends byline customization providing two settings that allow you to prepend and append any string — even HTML code! — to your bylines. We call them byline modifiers.