A group of internet service providers and developer Mozilla are playing a game of “he said, she said” with Congress over an internet security feature, setting up a potential fight in committee hearings over browsing data and how it’s collected or protected.

Chances are that the last time you visited a website, you entered a URL such as washingtonexaminer.com. That address is commonly referred to as a domain. That’s easy for people to grasp, but for computers, it means nothing except to be translated down into an internet protocol address used to direct to a specific website. Domain names are stored in what web infrastructure company Cloudflare describes as a “phonebook of the internet” or the Domain Name System.