Each user has a unique user name. When that user creates content, an 'Authored by username on publication date' item is automatically set up, and will be displayed on that piece of content. This is essentially the content's byline. Also, users with the correct permissions can change the authored by/ publication date information (on the Authoring information when editing content).
The Authored by username also determines the blog where a blog post will appear.
For example, if there are 2 authors of content for the site, their usernames should be their actual names:
John D. Rockefeller
When they are logged in and create content, the content will be published with something like this at the top:
Submitted by John D. Rockefellr on Fri, 12/9/2011 – 11:54
A site editor can change this Authoring information if necessary, to match the actual author. But the Author's name must be an actual Drupal user's name. If that user doesn't exist, then the site editor will have to create an account for them.
This authoring information is currently set to appear for Blog Post and Story content types only.