Party Sync for WoW was detailed by Blizzard today on their blog, outlining several items.
Once activated, all party members become aligned to the same quest and phase. You can also temporarily adjust your party so that higher level players will be able to quest and experience outdoor content with lower level players.
You’ll also be able to replay some quests,
“You’ll also have access to a “replay quest” feature that allows players who have already completed certain quests to replay them with friends who haven’t for rewards that are appropriate to their current actual level, regardless of the original level of the quest. Quests can be replayed for rewards once a day.
While most quests can be replayed, there are some exceptions. Repeatable quests, such as dailies and World Quests, can’t be replayed. We’ve also excluded some quests with story implications from being replayed. These are determined on a case-by-case basis, and may include quests like the Demon Hunter starting zone quests, or quests where you might choose to betray the Warchief (how could you!).”
Instructions to set up Party Sync are below. Check out the full post here.
Invite and accept players into a party.
Open your Map & Quest Log (hotkey: M).
Click Start Party Sync in the lower-right hand corner.
Have all partied players click Accept on the Party Sync confirmation dialogue box.