The "Subpage Default" is your default sub page.  The "Style Guide" page has been setup to display your site default styles.

The checkbox "Hide Page Title" removes the title from the page and the optional Header Sub Heading field (page description).

• The index.php is your home template and assigned automatically to your home page.  This templates operates the same as your default template.

Content > Link Lists  > "Alert Bar"

If a link is assigned to this link list it will display as an alert on the home page.  The description field is used for the text and the link is optional.