An SSL Certificate takes the information that your users provide and encrypts it, so that only a web server can decrypt it and understand it. So as the information on the web is transmitted via HTTP language, your data is not protected, as HTTP itself is not secure. The SSL Certificate takes your information, encrypts it, and passes it securely to the server where the website is hosted, or directly to the payment processor. On the merchant’s server, or on the payment processor’s side, the SSL certificate receives the encrypted HTTP information, decodes it, and safely performs the action you requested (logging you in, processing a payment, etc).
In this way, the SSL Certificate turns your “HTTP” connection into an “HTTPS” (secured HTTP) connection and protects your data. With an SSL Certificate, your information is protected and safe.