Firebox Type

Flush hearth
A Flush hearth is the most common construction for a fireplace. The floor of a Flush Hearth Fireplace is either flush with the hearth, or flush with the room floor.In this application:
Raised Firebox
A Raised Firebox is when there is distance between the firebox and the hearth or floor. In this application:
Raised Hearth
A Raised Hearth is when the hearth is higher than the floor of the fireplace.
Hole In Wall / Firebox Without A Hearth
A firebox without a hearth is when the firebox is raised off of the ground and there is no hearth therefore it is actually a Hole In The Wall.