Apps may ask for permission to do things like post status updates on your behalf and gather your email address or other basic personal information that you have listed in your Facebook profile. This is almost always to get around having to input all that information again when signing up for a new app or service. And it’s actually very useful.
A good example of this is Instagram: You give Instagram permission to post photos you take to your Facebook account.
To be clear, these third-party apps are very explicit about what kind of information they’ll take from your Facebook profile before you give permission. But if you ever change your mind and want to unlink the app from your Facebook profile or alter what kind of information the app can access, you’ll have to jump through a few hoops.
Here’s what you do:
First, start by heading to the drop-down arrow in the top right corner, click that and select Privacy Settings.
Next, head toward the bottom of the page to the Ads, Apps and Websites section. Then select Edit Settings.
After that, you’ll see a section in the middle of the page titled: Apps you use. This is a running list of all the apps you have authorized to use your Facebook account. Next to the apps is an Edit Settings button. Click that.
Now you’re inside. You can see every app, website, and plug-in that has access to your account. Go through the list and remove any app that you haven’t used recently.
To remove an app, click Edit next to an individual app. You can then see exactly what the app has access to (post on your behalf, access posts in your news feed, etc.). To revoke access, simply click Remove app.
We suggest you remove any app that hasn’t been used in six months.
Read more: http://www.businessinsider.com/facebook-app-privacy-controls-2012-10#ixzz28rJt3ntI