Your foot!

To find out what is your feet type, wet your feet
then step onto a dry surface to get an imprint.
Now compare it with these diagrams...

There are two kinds of flat feet -- anatomical and functional.
People with anatomically flat feet are born with them.
Those with functional flat feet, however, have a natural
walking gait that causes the feet to flatten out or
'pronate' totally when they walk. This causes strain to the
feet and can lead to ligament and knee injuries.

Feet pronate a little during each step and this acts as
a natural shock absorber.

Feet’s anatomy is naturally arched and the feet do not
flatten out during walking so the feet do not help to
absorb shocks. Hence shocks are transmitted to rest
of the body and this can lead to pain and aches.