What is a Wildcard DNS record?

 https://kb.porkbun.com/article/94-what-is-a-wildcard-dns-record

A wildcard DNS record is a record that answers DNS requests for any subdomain you haven't already defined. You can create wildcard A records and CNAME records by entering an asterisk (*) in the Host field when creating a DNS record.

For example, if you create the wildcard A record  *.goosehollow.design and someone visits https://abcdef.goosehollow.design, their request will resolve to the IP address you specified as the answer.