See the first link for a reasonably typical high-heel shoe. Notice how, inside the shoe, the place where the heel of the foot goes is tilted. Such a tilt forces much of the body's weight to jam into the toe area of the shoe, and is a large reason why they can be uncomfortable to wear.

Now think about the fact that anyone with decent balance can do some limited walking about in bare feet using heels only (the front part of the foot is tilted up and doesn't touch the ground). So imagine a shoe having a horizontal (a.k.a. "orthogonal") portion for the heel of the foot to rest, while the rest of the shoe tilts downward. Thus a much smaller amount of the body's weight is directed at the toe area, and in fact the toe area doesn't have to have a flat area on the ground; it can be edge-like at the ground.

The second link shows a MEN'S shoe that appears to have a reasonably flat place in it for the heel to rest. High shoes for men are typically called "elevator shoes" and this could be an extreme example of that (the page where I found it indicates almost no one wears them any more).
-- Vernon, Feb 11 2016

Typical high heel shoe https://pbs.twimg.c...ZkB85H_400x400.jpeg
As mentioned in the main text. [Vernon, Feb 11 2016]

High shoe with moderately flat internal area for the foot's heel http://ichef-1.bbci...6-0013-adetail1.jpg
As mentioned in the main text. [Vernon, Feb 11 2016]

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