Facebook Ads - A Facebook Ad is an ad to promote your nonprofit’s marketing message. If you’re promoting a Facebook Page, stories about specific Facebook users liking that page will be included in the ad. If your promoting an external URL, you can choose to also display and social activity about that URL next to the ad. These ads can be can be targeted to a subset of all Facebook users.
Sponsored Stories - A Sponsored Story is where you promote existing Page updates and stories from Facebook users that mention your business. The content for Sponsored Stories is derived from these updates and stories. Like Facebook ads, they’re only visible to friends you’ve already shared this information with. These ads can be can be targeted to friends of Facebook users who have liked the Page or use the App your are promoting.