A Secure Sockets Layer (SSL) certificate is a file installed on your webserver that makes the protocol used to access your website HTTPS instead of plain old HTTP. Since late 2016, Google has mounted a campaign to encourage the use of secure protocols, including it as a ranking factor in their search algorithm, marking any websites that use passwords as insecure (Chrome 56 onwards), and have future plans to display the HTTP security indicator as the same red triangle that is used for broken HTTPS.