The Facebook SDK for iOS provides various methods that your app can use to implement sharing.
The Facebook SDK for iOS provides a way to publish to a user's timeline with the Graph API.
The Facebook SDK for iOS provides hooks into the iOS6 share sheet so your app can use a native share dialog if the user has an iOS 6+ device.
The Facebook SDK for iOS provides methods for integrating with the Feed Dialogs, that publishes posts to News Feed.
If your app has Login with Facebook, people can find it through the Facebook for iOS app.
The Requests Dialog that is used by a user sends out notifications to one or more friends.