Dazar'alor is King Rastakhan's palace in Zuldazar. The Great Seal, in its interior chamber, serves as the Horde's embassy on Zandalar and includes some portals to each major city and expansions, profession trainers, bank and guild banks, transmogifier and a mission table.
In the Battle for Azeroth beta, there was an Unknown Device in Dazar'alor that served as a portal to the Chamber of Heart. It dated back further than the Zandalari knew. It was removed during beta.
This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials.*
It is likely that Dazar'alor translates to "Dazar's temple", with Dazar referring to the first king of the Zandalari, and with the Zandali word "Alor" possibly meaning temple or altar.
^Quest:The Word of Zul: Dockmaster Cobo says: He was wrong. Oh there was damage, but Zul fled, with our fleet, and started a few wars. Those of us who stayed, endured. We rebuilt. Because THAT is what it means to be a Zandalari.