Viewing your models as a silhouette form is useful for evaluating their overall form and proportion without the distraction of interior detail and shading.
The sculpting tools can still be used while the model is displayed in this fashion to adjust coarse details along the perimeter of the form during the formative stages of sculpting. For example, to assist in making the form match an image you’ve imported on an image plane:
Models in the view appear as a silhouette.