As expected, Facebook has tied up with Skype to provide video calling feature to all Facebook users.
The following are the steps by which you can have this feature up and running:
1) Go to this link: http://www.facebook.com/videocalling
2) Once you have installed the app, you will see an icon on top of every chat box. Click on it to start chatting.
Google+ also has the same feature called hangout which allows multiple users to start video conferencing between them.
Here is quick comparison between Facebook video calling and Google hangouts
1) Facebook video calling is one to one video calling whereas Google hangouts allows you to video chat with multiple people.
2) Facebook video calling is based on peer to peer communication whereas Google hangouts is completely browser based.
3) Google hangouts is based on Google+ circles whereas Facebook video calling does not apply to a Facebook list.