This skips all the content before the previous expansion to give players the most modern experience from a quest design POV (and to make sure the players are connected with the current storylines). It also ensures new players have a shorter leveling ramp—Blizzard says it will be as much as 70% shorter than it is currently to get from level one to the cap.
Frankly, the aspect of Shadowlands I'm most excited about is an overhaul of the leveling system—something that wasn't a part of this demo in a major way. This kind of breaks the rules of a hands-on article, but I want to take an opportunity to talk about it and why I think it's interesting, regardless, since it came up in my interview with WoW developers.
Alpha Beta PTR Vanilla 1.1.0 1.2.0 1.3.0 1.4.0 1.5.0 1.6.0 1.6.1 1.7.0 1.8.0 1.8.4 1.9.0 1.10.0 1.11.0 1.12.0 Burning Crusade 2.0.1 2.0.3 2.0.4 2.1.0 2.1.2 2.2.0 2.3.0 2.4.0 2.4.3 Wrath of the Lich King 3.0.2 3.0.3 3.0.8 3.1.0 3.2.0 3.2.2 3.3.0 3.3.3 Cataclysm 4.0.1 4.0.3a 4.0.6 4.1.0 4.2.0 4.2.2 4.3.0 4.3.2 Mists of Pandaria 5.0.4 5.0.5 5.1.0 5.2.0 5.3.0 5.4.0 5.4.7 Warlords of Draenor 6.0.2 6.0.3 6.1.0 6.2.0 Legion 7.0.3 7.1.0 7.1.5 7.2.0 7.2.5 7.3.0 7.3.5 Battle for Azeroth 8.0.1 8.1.0 8.1.5 8.2.0 8.3.0 Shadowlands 9.0.1
Shadowy Tormentors inhabit this dimension, and emerge from it to torment death knights such as Koltira Deathweaver. The Lich King originally kept them at bay, but after the Knights of the Ebon Blade left his service, the tormentors are now loose upon them. He even appears in the World of the Dead, as he calls it, riding a frost wyrm during  The Power to Destroy.
During the Burning Legion's third invasion, the Knights of the Ebon Blade traveled to the Shadowlands to acquire the Aggregates of Anguish, five tormented essences of powerful souls - Admiral Proudmoore, Soulbinder Nyami, Grand Empress Shek'zeer, Grand Apothecary Putress and Archmage Arugal. Salanaar required these to conjure the Steeds of the Damned for the order's new Horsemen.
Keep raising the level cap with no changes to the leveling experience up to that point. This leads to ever-lengthening leveling ramps that make it extremely difficult for new players to get to current content. That's because each expansion adds another several dozen hours to how long it takes to get from the start to being able to play with friends in the endgame. (Final Fantasy XIV has this problem to some degree, even though it's nowhere near as old as WoW.)
The origins of the Shadowlands remain uncertain, but they have existed ever since mortal life first arose in the physical universe. They span all worlds, including Azeroth, on which Icecrown serves as an anchor to the Shadowlands. There are those who believe mortal souls are drawn into this dark place when they die, remaining there forever. Others hope their souls will go on to a brighter place rather than languish for eternity within the cold confines of the Shadowlands.