If you run several web applications on a web server, it is relatively annoying to keep separate processes running for each individual subdomain, which fetches the required SSL certificates in good time before the expiration date and carry out the verification process for each website.
For this reason, there are wildcard certificates, i.e. certificates that cover your own domain including all subdomains in one certificate. This certificate can then be stored centrally and used for all subdomains without further actions. I'll explain how to do that now. Read more