Among the many threats to your computer, one is called 'ransomware', a type of program which can insert itself into your machine and then ENCRYPT the data on it, so you cannot access your own machine. Then you get a notice to PAY money in order to get the decryption key.
Obviously this is one of a billion reasons why you should be careful where you surf, what emails you open, and backup your data daily. Learn to clone, too, as often only a clone of your drive can get you up and running when Windows tanks.
So: bleepingcomputer.com has a number of really gifted computer guys who help folks out. One of their primary specialties is ransomware. So for the latest article on it, and feel free to go over there and ask questions. I tried to offer them money as a donation, and they wouldn't take it.