Digital security on a limited number of servers and subdomains.

They are the simplest way with a digital certificate to guarantee the authenticity of a domain and all its subdomains (first level). (*)

(See the necessary documentation here)

(*) For example, a *.test.com certificate can be used on test.com, but not experience.example.test.com. A simple TLS/SSL certificate issued to test.com would only work on test.com. For it to work on www.test.com and example.test.com, it would be necessary to purchase additional SANs, related to these addresses or additional simple certificates.