The expansion adds a new continent named Broken Isles. It's never been playable in World of Warcraft before, but was referenced in Warcraft 3.
What's more, Legion raises World of Warcraft's level cap to 110 and introduces a new class called Demon Hunter (read on for more details on the new character). There are also new dungeons and raids to explore, as well as new artifact weapons and an Honor System.
Read more of "New WoW expansion introduces new class, raises level cap, and more" at GameSpot.