And what do they do exactly? I'm not familiar with waystones.
They may be referring to waystone mods, which is essentially an interactable stone pillar where multiple can be set up as an easy/quick transportation network. They could be named, you interact with any to select which other ones to teleport to, and you go to that place in an instant.
That said, it's been a popular mod, and Mojang stated not adding community-made mods anymore, so waystones very likely won't be officially implemented.