Due to the nature of the tor network, relays aren't a secret. They need to be public so clients can independently choose which to use.

You then get people who operate lists of all relays e.g. https://www.dan.me.uk/tornodes

There's probably a good reason for using a "full" list, but I can't think of one off the top of my head. That site at least offers both and just about explains the difference.