DOF or Depth Of Field is a commonly used technique in photography where you can precisely focus only part of the face or object you are taking shot of. Let's recreate this using Photoshop.
If you are using Facebook social apps for watching videos, reading content and you don't want your friends or everyone to know about your activity, you can turn this off.
It's highly recommended to protect your computer against Virus, Malware, Spyware and other potential threats. Microsoft Security Essentials is one of the better, free solutions.