Dream Orbs are Stat enchants like Runes, but stacks with them that Dream Weavers can create. They go into the Helmet, Neck, Shoulders and Cape slots and have different level requirements dependent on the type of Dream Orb.
They provide a random chance at one of 20 different combinations per gear slot, per gear level/tier, per type of Dream Orb.
They are tradeable and require a whole bunch of Dream Ribbons and Coruscating Ethereal Shards.
Click below for more information on Dream Weaving and how to level up the profession.
Dream Orb Stat Sheet
All combinations are listed so that you can hopefully make better-informed decisions about whether to risk losing your second-BiS stat in order to attempt to get the BiS stat, which may only be a +1 main stat difference.