Total: Number of people who have seen any content associated with the page

Organic: The number of people who visited your page, or saw your page or one of its posts in news feed or ticker. These impressions can be fans or non-fans

Viral: The number of people who saw your page or one of its posts from a story published by a friend. These stories include liking your page, posting to your page's wall, liking, commenting on or sharing one of your page posts

Paid: The number of people who saw a sponsored story or sponsored ad about your page or its posts