An example of a single domain is: www.networksolutions.com
An example of a sub-domain is: security.networksolutions.com
If you have only a single domain to secure, you can use nsProtect™ Secure Basic, Advanced or Extended Validation (EV). If you need to secure 3 or more sub-domains, the Wildcard certificate is your best value.
There is no Wildcard for EV Certificates.