I would assume that your house floor is resting on a poured concrete
floor, and the threshold is part of the 'French door' frame.
Can you check from the basement?

It does look like your entrance has 'double doors'.......nice
piano........Sky
wrote:
Hi,

What you are seeing here http://i.math.drexel.edu/~pg/step.jpg is the
entrance into my hose from my porch. What you see is a concrete step,
then a wooden threshold about 2" high, and then the hardwood floor is
the same level as the top of the concrete step.

What is the purpose of the threshold?

(My initial idea was for water protection, but then I realized that the
porch is several feet above the ground and the concrete step is almost
a foot tall, so that can't be it. Could it be that the door was the
wrong height when it was originally bought?)

Thanks!

Aaron Fude