An area is just a specific part of the country, as governed by the USEA. It splits things up in the way that USEF 'zones' do for the sake of points, area committees, etc.
I live in Area 1 (alas, no pictures from here), was a working student in Area 2, and am moving to Area 3 next month to be a working student for a different rider.
Here are some Area 2 pics - this is Loudoun Hunt Pony Club Horse Trials (say that five times fast) at Morven Park, BN:
From MCTA at Shawan Downs, Novice:

(awful leg. Ew.)