Welcome to Drupal 7 - No front page content has been created yet
When you initially install Drupal 7, your homepage will show the following message:
This is because you have yet to promote anything to your front page.
When you begin to create your first articles in Drupal 7, they will show on your frontpage. As you continue to write more articles, your older ones will be pushed further down the page and replaced with newer content.
There are various settings you can adjust for your frontpage. For example, you can set how many of these articles to show, and you can also change how much of those articles show (for example, the preview of the article). You also don't even need to show articles, you can show any specific piece of unique content you've created on your frontpage.