SSL stands for Secure Sockets Layer and describes a method of encrypting the data traffic between a browser and a website so that no hacker can read or change the data. You can recognize a website protected with SSL by the https:// in the address line instead of http://.
Encryption is carried out using an SSL certificate. This is issued by a third party such as Symantec and set up on the website. An SSL certificate contains information such as the publisher and owner of the certificate, as well as a key with which the data traffic is encrypted. In most modern web browsers and operating systems, the publisher of SSL certificates, also known as certification authorities, are entered. With the aid of these entries, it can be checked while establishing a connection whether the SSL certificate is valid and was issued by a certification authority.
When calling up a website that uses an SSL certificate with "Extended Validation", the address line is also colored green. A website visitor can therefore see immediately that the site owner is authenticated.
When using an SSL certificate with "Extended Validation", the browser's address line is colored green to signal trustworthiness to website visitors. A thorough check of the ordering party is therefore carried out before issuing SSL certificates with "Extended Validation".
Detailed information about the various SSL certificate types can be found under "What types of validation are available?".