You can now keep up with your Facebook friends, no matter what you are doing on your PC, thanks to the new Facebook Messenger for Windows. Whether you're surfing other websites or using another software, you don't have to click away to stay connected with your Facebook friends.
The Facebook Messenger lets you use Facebook without being on www.facebook.com and allows you to easily find out about new comments, photo tags and more as soon as they happen.
While you browse the internet or use other applications on your computer, you can:
==> Chat and message with your friends on Facebook
==> See the latest updates from your friends in ticker
==> Get quick notifications about what’s going on
How To Download Facebook Messenger for PC
==> Go to http://www.facebook.com/about/messenger and click the "Install Now" button
==> Click Save File to set up Facebook Messenger.
==> Run the downloaded file.
Check this Facebook help Page for more info.