Even though a modern server architecture is used, Classic servers won't have the same features that current World of Warcraft does. There won't be cross-realm servers or Looking For Raid and Dungeon Finder automatic party matchmaking. There are still a lot of questions about how the team will tackle it. This endeavor is being undertaken by an entirely separate team at Blizzard from the one working on World of Warcraft and its next expansion.
Classic WoW is the highly anticipated, upcoming (re) release of the original, first World of Warcraft version, known as Classic and by it's other popular ice-cream like name: Vanilla WoW. Dubbed Retail Classic, or Official Classic by the playerbase - it was finally announced by Blizzard in November 2017, after a lot of pressure from the Private Server World of Warcraft community, since the latter's shutdown of the most popular Private Server called Nostalrius which featured the first WoW version in two separate PvP and PvE servers.