Purpose of Private DNS server
As the name suggests, a Private DNS server appears to be something personalized. It links your network and the Domain Name System server, protecting data from being intercepted by third parties. They are DNS networks that are not linked to the Public DNS. Consider it a Private library with a small collection of books. This has both advantages and disadvantages. Yes, you will be unable to read certain types of books. Nevertheless, there is one advantage: no one will know what you are reading because your library is secret.
Furthermore, we refer to Private as DNS over TLS (Transport Layer Security) or DNS over HTTPS (Hypertext Transfer Protocol Secure). This is because when you use DoT (DNS over TLS) or DoH (DNS over HTTPS), all DNS queries are encrypted. This makes it far more difficult for malicious third parties to monitor your online activity.