Area
An area is a subdivision of an explorable region. Most locations are referred to by their region name, but some regions contain a smaller location that is labeled in the world map or in quest lore. For example Dead Man's Holyland in Silent Woods or Grand Marsh in Northeast Glorious Imperial Territory, but also includes instanced areas like the Snow Storm arena.
These smaller locations are marked by 
on the interactive maps throughout the wiki.
Instances
Instances are locations that are opened for a specific party, character level range, or can be entered with other players without sharing a party.