A secure socket layer (SSL) encrypts communication between users and a website. This means that sensitive data including usernames, passwords, and credit card information can be sent without the risk of interception. You can see when a website is using a SSL as a padlock is displayed on your browser search bar. You will also see that a pages web address will be prefixed with HTTPS rather than HTTP. SSL is also very important to Google, rankings are higher for secure sites. Your site might appear as unsecure to your visitors and they will be warned before choosing to visit.