Technically, anyone can create their own SSL certificate by generating a public-private key pairing and including all the information mentioned above. Such certificates are called self-signed certificates because the digital signature used, instead of being from a CA, would be the website’s own private key.
But with self-signed certificates, there’s no outside authority to verify that the origin server is who it claims to be. Browsers don’t consider self-signed certificates trustworthy and may still mark sites with one as “not secure,” despite the https:// URL. They may also terminate the connection altogether, blocking the website from loading.