When working with models, the pose can determine which genre of photography you are shooting. Professional models specializing in specific fields will know how to pose, but amateurs will not know. Then it becomes the photographer's job to ensure the pose is appropriate for the client, whether it is a magazine or a designer or otherwise.
The best way to illustrate the difference between poses is to state it in terms of fashion versus glamour. Models who have worked in the porn / glamour industry often arch their back more than fashion models do. This highlights features of the body that are more popular in glamour and men's magazines. Glamour models often tend to pose with their mouths open because the brain associates that with sex, even if the model is clothed in the image.
Fashion models should arch their back less than glamour models should. Fashion often utilizes more interesting poses, maybe bending sideways or forming odd angles. This catches the viewer's eye, and makes them interested in the product: the clothing. Fashion models can pose with an open mouth, but only slightly open. It should look relaxed if the mouth is open. Photographers need to watch this and tell them, "close your mouth" if it becomes too much about the model and less about the clothing.
Fashion photography is much more about creating height in a model than glamour photography is. For this reason, it is important to pose the model so that you can shoot slightly upward at them, even if they are already tall. It is also the photographer's responsibility to ensure the model is not doing something with the pose that makes her look shorter. Elongating the neck, legs, and arms make the model look much taller.