Ransomware is the name for malware that once installed on a computer, often unwittingly through clicking on links in spear phishing emails, encrypts and locks all of the victim’s data.  The cybercriminal then threatens to destroy the data unless a bounty is paid.  Last year we  experienced two massive ransomware attacks against millions of computers around the world.  These were the infamous WannaCry and Peta ransomware attacks.  While companies and government agencies are often the targets of ransomware, individuals are also targeted by this malware, as well. In fact, according to a recent report by the security firm Malwarebytes, ransomware attacks against consumers increased by 90% in 2017 from the previous year.
TIPS
Often ransomware attacks as well as other types of malware attacks are spread through phishing emails that lure unsuspecting people into clicking on malware infected links or downloading attachments tainted with malware.  As I am constantly reminding you, never click on links or download attachments until you have confirmed that they are legitimate.
You also should update all of your electronic devices with the latest security updates and patches as soon as they become available, preferably automatically.  Many past ransomware attacks exploited vulnerabilities for which patches had already been issued.
As for protecting yourself specifically from ransomware, you should back up all of your data on at least two different platforms, such as in the Cloud and on a portable hard drive.