Think of it as shorthand for a list that expands to be infinitely large. [0]
People would consider a blacklist that includes ` * .example.com` to be a list that contains all potential subdomains of `example.com`. With ` * ` being seen as shorthand.
E: Spaces around the asterisk added to avoid HN formatting.
[0] Technical limitations aside, especially in the context of URL matching since URLs have a maximum character length.
