GeoTrust, as a Certification Authority, is the second largest provider of certificates in the world with more than 100,000 customers in over 150 countries.
GlobalSign is the most established Certification Authority in Europe and the fourth largest SSL provider worldwide, with more than 50 billion SSL certificates in action right now.
Green address bar or Green bar of trust
The address bar of the most common browsers (Internet Explorer, Firefox, Chrome, Safari and Opera) turns green when the website is protected by anEV SSL certificate. The green bar will also show the CA that issued the certificate, plus the legal company name who own the website. This provides visual proof of your website security and creates the most trustworthy environment for your customers to transact on your website, and confidently do business with you online.
gTLD is the abbreviation of generic Top-Level Domain, which is also often called "domain name extension". Generic top-level domains are different from "country code" top-level domains (such as .fr, co.uk, .de, .nl, etc.)