The ten kinds of foulness are corpses in different stages of decay:
This set of meditation subjects is especially recommended for removing sensual lust. So the whole purpose of doing it is actually to remove the misunderstanding of the attractiveness of the human body by contemplating its eventual fate. They can be observed without repulsion, but it takes time for a meditator to get there. When and if they arrive to no repulsion, it may mean they no longer cling to form.