This is a picture of a fake security alert. If it appears on your screen do nothing. Don’t click on any of the buttons as it will only get you into deeper trouble.
If you have Malwarebytes installed, run it immediately to rid your computer of this scam. If you don’t have Malwarebytes installed you probably won’t be able to get on the Internet because this infection changes browser settings. You can download Malwarebytes from a clean computer to a flash drive, then install and run it to clear the problem on your infected machine.
If this is all too confusing then you can consult a computer expert.