We all see this button nowadays. 
Many websites now have the option of signing up or logging in using your Facebook account credentials. While this is very convenient, many of us don’t want other sites to post on our timeline without us knowing what it is. There’s a way to make sure if anything does get posted, that only YOU will be able to see it.
1. For example, if we go to Etsy.com and want to log in with Facebook, the following window will pop up. Read the info in the red boxes.
2. Click on Public and then click on “Only Me” so only YOU can see stuff on your Facebook timeline posted by this site.
That’s all there is to it. Now anytime there is a post by Etsy (or whatever site), they will appear on your timeline and in your News Feed but won’t be visible to anyone else.
However, if someone else makes a post and tags you through the site, that will, by default, be posted on your timeline. But there’s a way around that, too! Read this post on how to make it such that photos or posts that you’re tagged in, have to be approved by you before they post on your timeline.