Sorry if this analogy has already been thrown at you dozens of times, I like to think of DNS like an address book for the internet. On a traditional phone, I can't just type in someone's name, I have to type in a number. Without DNS, the internet would be like that, accessing any website would require recalling and typing in the IP address. But DNS translates domain names (hence Domain Name System), the part of the URL leading up to .com, .ml, etc, into the proper IP addresses for you.

Unless you self-host, the DNS service is hosted on someone else's server, and many devices default to communicating with the DNS server in plain text. Which is why you want to trust your DNS provider since they can keep a list of which sites you visit. And DNS over HTTPS mitigates the possibility of interception by encrypting your DNS requests.