Starting today, Mozilla is activating the DNS-over-HTTPS security feature by default for all Firefox users in the U.S. by automatically changing their DNS server configuration in the settings.
DNS over HTTPS DNS over HTTPS is a protocol for performing remote Domain Name System resolution via the HTTPS protocol. A goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data by man-in-the-middle attacks by using the HTTPS protocol to encrypt the data between the DoH client and the DoH-based DNS resolver.
So what does this mean in laments terminology? Short answer increased privacy and security. This privacy-focused technology makes it harder for man-in-the-middle attackers, including your ISPs, to manipulate DNS queries, eavesdrop on your Internet connection, or learning what sites you visit.