Basic SSL Certificates will support one website on one domain name in one certificate.
A certificate issued for iwebz.net can only add HTTPS support to iwebz.net and www.iwebz.net, but NOT cloud.iwebz.net
A certificate issued to cloud.iwebz.net can only be used for cloud.iwebz.net and NOT www.iwebz.net
Wildcard SSL certificates will support all subdomains of one domain name in one certificate.
A wildcard certificate issued for *.iwebz.net can also be used for www.iwebz.net, links.iwebz.net, and cloud.iwebz.net
Multi-domain or UCC/SAN certificates can support multiple domain names in one certificate.
A multi-domain certificate for iwebz.net and iwebz.in can support www.iwebz.net, iwebz.net and www.iwebz.in
A multi-domain wildcard certificate supports multiple domain names and all subdomains of each domain name.