What is the difference between a Flame Druid and a Shaman?

[Drahliana-earthen-ring (Drahliana)]

@Ahlyaani-moon-guard

Leveling one of my alts through Hyjal, a question struck me:

Just what is the difference between a Flame Druid and a Shaman?

Is there a difference? Or is there just a labeling issue? Is it a Druid that is just multiclassing into Shaman as well?

The latter is a follower of elements and a bridge to the spirit world, the former is a corrupted Druid who has become an agent of the Old Gods. under the tutelage of the corrupted ArchDruid Fandral Staghelm.