Domain Validated is where the CA (Certificate Authority) checks the right of the applicant to use a specific domain name. No company identity information is vetted and no information is displayed other than encryption information within the Secure Site Seal.
Extended Validation (EV) SSL certificates provide the ultimate protection from online fraud. Once you install an EV SSL on your site, any visitor using a high-security browser will see the address bar turn green. This visible sign increases customer confidence as they could visibly see that your site is authenticated and trustworthy.
Organization Validated is where the CA (Certificate Authority) checks the right of the applicant to use a specific domain name PLUS it conducts some vetting of the organization. Additional vetted company information is displayed to customers when clicking on the Secure Site Seal, giving enhanced visibility in who is behind the site and associated enhanced trust.
A Wildcard SSL certificate secures your website URL, and an unlimited number of its subdomains. For example, a single Wildcard certificate can secure www.yoursite.com, blog.yoursite.com, account.yoursite.com, etc. WildCard SSLs can be either domain or organization validated.