A Keylogger is a Program or hardware that record all the typed material.

"Keystroke logging (often called keylogging) is the action of tracking (or logging) the keys struck on a keyboard, typically in a covert manner so that the person using the keyboard is unaware that their actions are being monitored. There are numerous keylogging methods, ranging from hardware and software-based approaches to electromagnetic and acoustic analysis." 
According to Wikipedia.


Types Of Keyloggers::


There are two main types of keyloggers:
1: Hardware
2: Software


How can they be used for hacking.


For hacking Software Keyloggers are used which are installed on Victims computer manually or remortely and then the report of the the Keylogger is presented to the Hackers in form of Email or it is uploaded to specific FTP account of Hacker.


Where Can i Get a Keylogger?


Most of Keyloggers are expensive commercial one. But I will put some free and cracks of Keyloggers soon which are free!!!!