Wildcard SSL certificates are use to secure multiple subdomains accross a single domain.  Example : *.sslcertificate.ch can secure this subdomains admin.sslcertificate.ch, test.sslcertificate.ch, wildcard.sslcertificate.ch…Etc.
Wildcards provides a 256 bits RSA with the robust Digicert Secure site pro providing Up to 512 bits RSA & 384 bits ECC.