The front page is the initial page seen by someone reaching a Moodle site. It is not the home page for a course or classroom, but rather for the whole site.
The site settings determine which user roles can reach it. For example, the demo.moodle.org allows visitors (guests) to see it's front page and asks them to log in. A user clicking on the course is taken to the "Returning to this website" Moodle login in screen. Other sites may require a login before showing the front page.
Many functions of a front page are similar to those found in a course. The administration block will allow topics to be added to a Front Page.