What is a Certificate Authority?
A Certificate Authority is a trusted entity, responsible for issuing and revoking ssl certificates.
For this, Certifying Authorities (CA) have a variety of methods to verify the information provided by individuals or organizations.
Established Certificate Authorities are well known and trusted by browsers. Browsers extend that trust to verified digital certificates such as DigiCert, Thawte, GeoTrust, RapidSSL, and Entrust.
An SSL certificate serves as a credential in the online world. Each SSL certificate uniquely identifies a specific domain and a web server. Trust of a credential depends on confidence in the organization that issued it.