Question: 
What is the boundary between the light and dark regions on the Moon Called?
Answer:
The terminator.
Question:
If the photo is of a waning moon, was the photo taken from the Northern Hemisphere or the Southern Hemisphere?
Answer:
The lighted part of a waning moon continues to get smaller each day until it reaches the New Moon phase (no lighted part is seen). In the Northern Hemisphere, the Moon is seen in the southern sky and its terminator moves toward the left (east).
The photo is of a waning moon as viewed from the Northern Hemisphere.