What is a green (EV) SSL?
Extended Validation Certificate
Certain SSL cerificates utilize what is known as "Extended Validation".
EV certificates require verification from the business that requests one. Only after a predefined set of checks and validations is completed will a EV certificate be issued.
These certificates are designed to provide a higher standard of assurance for visitors to authenticate the business behind the domain. The green HTTPS address bar is exclusive to EV SSL certificates and reassures website visitors that they are interacting with a verified business on a secured domain.
This basically means that all communication between your browser and that website is encrypted and that the certification authority has confirmed the website is owned or operated by a business that is legally organized under the jurisdiction shown in the certificate and on the Security Status bar.