As a Legion Legendary. All legendary bonus effects are passive "Equip" effects. The effect is based on the classes, roles, and Specialization.
At the beginning of Legion, only 1 legendary item can be equipped at a time. Over time, as the expansion progresses this cap will be increased.
While the legendaries are rare drops, they are not fully random - there will be ways to target specific items.
Legion legendary procs/effects will be disabled in PvP.
If the slot for the item is transmoggable, you can transmog these legendaries to other appearances, and vice versa (unlike legendary items from previous expansions)
All Legion legendaries are Bind-on-Pickup, and cannot be sold, traded or listed on the Auction House.