Usually DNS queries sent by your computer to the DNS resolver are sent over an unencrypted connection. Anyone with access to your network can eavesdrop these queries.
By using DNS over HTTPS, abbreviated as DoH, your privacy is safeguarded as the traffic is encrypted.
Nowadays most internet traffic is sent encrypted (which provides additional privacy to the user), like websites using https instead of http. This is why DNS over HTTPS was developed and why it was implemented at Belnet.