www and @, or a single subdomain, such as example.com and test.example.com, is 1 domain name
Multiple domain names are bound to the same certificate. By default, three domain names are bound, such as a.com, b.com, and c.com (excluding www).
Protect all subdomains of the same level as a wildcard domain name; for example, *.xyz.com supports all subdomains of the same level as a.xyz.com and b.xyz.com, but does not support aaxyz.com