Keylogger is a software that's used to steal username and password, keylogger is not only used to steal facebook username and pasword, it can be used to steal anything which use username and password, like blogger, friendster and etc.
Keylogger work by monitoring the keyboard, every keypad or button typed by user will be recorded and be saved in keylogger, that's cool right?
To activate this hacking software you just need to install this software on computer.