What's fantastic about this new system is that quests and monsters will always match your level so you can focus more on the story of each zone.
Once you reach level ten you should be most of the way, if not completely, finished with your starting zone. From there, several new expansion zones become available to you. A few years ago, Blizzard introduced limited dynamic level scaling for all of WoW's old zones and expansions. Instead of having a strict level requirement, now zones have level ranges that always adapt to suit your character's level. What's fantastic about this new system is that quests and monsters will always match your level so you can focus more on the story of each zone. Your choice of which expansion to level in (Battle for Azeroth is the default for new players, for good reason—as  the most recent expansion before Shadowlands, it’s the most modern) will take you from level 10 to 50, when you’ll start in the Shadowlands.