In the Shadowlands, each zone will have one of four Covenants: the Kyrian, Venthyr, Necrolord or Night Fae. You'll be introduced to them through the Shadowlands story and at max level, you'll get to join one of them and get access to their rewards, including a class-specific Covenant ability, a Covenant movement ability, unique transmogs and more!
ETA: 4 Hours
(Torghast unlock + 4 Hours)
Pre-order is a guarantee that you will receive your service as quickly as possible and without queues. At the start of Shadowlands there will be huge queues for services due to the large number of orders, pre-order will help you avoid the queue and be one of the first!