Wildcard SSL Certificate

What is a Wildcard SSL Certificate?

Easy to manage and flexible, a Subject Alternative Names (SANs) secured Wildcard is a top choice for organizations managing multiple sites hosted across numerous subdomains.
With a DigiCert Wildcard, you can issue copies of your certificate on as many servers as you want, each of which is assigned its own private key. Protect additional domains by adding Wildcard SANs at any point during the lifecycle of the certificate (additional charge).

A certificate configured for *.example.com, will secure www.example.com, as well as mail.example.com, blog.example.com, and others. The asterisk is used to serve as placeholder for all possible subdomains.