Those are called worlds and you just finish the quests I'm whatever world you're in and then you'll be sent to Marleybone then mooshu the Dragonspyre then celestia the zafaria then avalon thenazteca then khrysalis then Polaris. Also for side worlds you'll be called to Meryl Ambrose and he'll give those quests to you so you can do grizzleheim wysteria and wintertusk. Also what I think you were trying to spell is "realm" and realms are different than worlds.
every time you complete all main quests in a world you get a spiral key this is used to travel between worlds also if you see any other people that have it means that is a side quest
it means that is a side quest