SSO is “single sign on”. DNS is “domain name service”, which is just a way to turn a hostname (like www.google.com) into an IP address. It’s sort of like a phone directory, but for the Internet.

The first time I visited there, I wanted to live there. Like this book I read in school when I was in third grade, where the kids hide out in the museum overnight.

You must mean this one: https://en.m.wikipedia.org/wiki/From_the_Mixed-Up_Files_of_Mrs._Basil_E._Frankweiler