Ransomware are the computer viruses that prevents you from using your computer unless you do something. Most common ransomware ask you to pay ransom (usually a fee or other makes you perform surveys) to get access to your computer.
Ransomware can gets installed to your computer by:
Once it gets to your computer, it will start doing its work either by locking your screen or encrypting your entire filesystem.
You should be very careful about which application you are installing and where you are downloading these application from.
If you are a victim of Ransomware attack you can report a Crime by visiting https://www.nomoreransom.org/report-a-crime.html