Facebook is world’s no. 1 social networking website which has users from all over the world. To use any feature of Facebook, you first need to login.
To Login at Facebook either go to Facebook.com and you will find login box at top, enter your email/facebook username with password or go to login page http://www.facebook.com/login.php and enter your information.
There are lot of other sites, forums too that allows you to login with your facebook account like Digg where you can login via your facebook account.
To add Facebook login to your website you can use Facebook API or use plugins if you are using WordPress, phpBB, vBulleting etc.
face is a way to rejoin and communicate with people