Audience: The number of total Page likes.
New Fans: The number of new Page likes received during the selected time period.
Lost Fans: The number of Page likes lost during the selected time period.
Organic: Page likes received from organic sources.
Paid: Page likes received from a Sponsored Story or Ad pointing to your Page.
For more information on Facebook metrics, please refer to the following FB developer resource: https://developers.facebook.com/docs/graph-api/reference/v2.8/insights