Not to leave behind in race , Apple has made changes in iOS now.. And few great stuff coming out in iOS8. And one is App Extensions.
Imagine “you have one specific requirement for your business & for that you just want to use existing iOS App or feature and want to enhance a little bit for your need” Previously it was not possible now you can extend functionality of existing system up to certain extent.
As Mentioned on Developer.apple.com “An app extension (or extension) lets you extend custom functionality and content beyond your app and make it available to users while they’re using other apps. You create an extension to enable a specific task; after users get your extension, they can use it to perform that task in a variety of contexts. For example, if you provide an extension that enables sharing to your social sharing website, users can use it to post a remark while they’re reading email messages or surfing the web. Or if you provide an extension that displays current sports scores, users can put it in Notification Center so that they can get the latest scores when they open the Today view. You can even create an extension that provides a custom keyboard that users can use in place of the iOS system keyboard.”
A system area that supports extensions is called an extension point. Each extension point defines usage policies and provides APIs that you use when you create an extension for that area. You choose an extension point to use based on the functionality you want to provide.
Extension Points are
Today:- Today is a Widget in common sense.. perform a quick task in the Today view of Notification Center
Share:- Post to a sharing website or share content with others
Action:- Manipulate or view content within the context of another app
Photo Editing:- Edit a photo or video within the Photos app
Storage provider:- Choose a document from among the set of documents the current iOS app can access
Custom Keyboard:-Replace the iOS system keyboard with a custom keyboard for use in all apps
you can read a lot more here.