A wildcard SSL certificate allows you to use https://*.yourdomain.com where * can be anything. If you purchased a certificate for secure.yourdomain.com and you attempt to use it on store.yourdomain.com, the web browser or SSL client will issue a warning stating that the SSL certificate and hostname do not match. That is because your certificate is bound to secure.yourdomain.com. However, with a wildcard certificate, you can use anything.yourdomain.com. These are useful when you have many hostnames to secure under a single domain.
