You know about keylogger?
Keylogger is a method to capture all the information that your are typing on your keyboard. Keylogger is one way that others people can capture all character that you are typing from your keyboard. It will be contain of your personal username, password, PIN number, secret answers, your mothers name information and all thing that belong of your personal detail. All this information are maybe it is very important and secret. Maybe it could be using on your personal banking info, Your credit card, your paypal or others document that really secret for you.
Keylogger is very common method that using to capture it. The most popular keylogger is using the software that installing automatically on your computer previously. It could be a spyware or virus that running on your computer. But nowadays the hardware keylogger is using to capture all character that you typing from your keyboard.
For full detail view in here : BEWARE OF KEYLOGGER