Explain Like I'm Five

so there are two aspects. as people have said it goes sorta reverse of the name. so there is the root operated by ican that directs to the top level domains like .org which directs to specific addresses like eff. Thing is there is stuff that is publically made available and internal ones and this has to do with where a person gets their directory. So people who work for eff likely have a dns provider in the list their machine uses (they can have one or many listed and it checks it in the order its configured in) that is from the eff. this allows them to find all the machines from eff. But if you are looking for machines there you will have a provider getting public machines from eff and that will only be a list of machines the eff wants to be publically available. As an individual you will use a dns that either you configured or was configured by some process you did. Like your isp will generally have one available and if you don't specify what to use in your config it will grab the information along with other network information from dhcp. The same process that you get your ip address with. You could go in though and change that (just realized I never did when I reinstalled my machine) and in addition software you run can override that. Like you can set dns servers to use in your web browser.