SSL certificates are the standard for securing your website. SSL is a transparent protocol, which requires little interaction from the end user when establishing a secure session. For example, in the case of a browser, users are alerted to the presence of SSL when the browser displays a padlock, or in the case of Extended Validation SSL the address bar displays both a padlock and a green bar. This is the key to the success of SSL – it is incredibly simple experience for end users.
As opposed to HTTP URLs which begin with "http://" and use port 80 by default, HTTPS URLs begin with "https://" and use port 443 by default.
HTTP is insecure and is subject to eavesdropping attacks which, if critical information like credit card details and account logins is transmitted and picked up, can let attackers gain access to online accounts and sensitive information. Ensuring data is either sent or posted through the browser using HTTPS, such information is encrypted and secure.