The easiest explanation for how an SSL Certificate works is that it safeguards transmitted data between a web-browser and the server the website sits on with guaranteed encryption for easy, safe and reliable browsing and internet shopping. When a customer enters a secured area, they can confidently enter login details, credit card information or other private information into the website without having to worry about the data submitted being hijacked by a hacker or other 3rd party.
Servers and browsers communicate with each other and serve information back and forth. Your browser requests a website to be displayed and the server responds with the browser request. Generally, when a browser (such as IE, Firefox, Google Crome etc) requests a server to display a website it does so over an unsecured http:// port 80.
When you purchase and install an SSL Certificate on the server, the communication between the server and the browser becomes encrypted via a negotiated handshake process using the familiar https:// on the secured port 443. The encrypted SSL handshake between browser and server happens discreetly behind the scenes without any type of interruption to the overall user experience. Depending on the various types of SSL Certificates implemented on purchase will determine the SSL indicators that show up in the browser.