Face mills cutter are for machining of surfaces that are perpendicular to the cutter axis, or the face of a part, primarily not for taking a very heavy cut. Face mills are used to get the precisely-flat surface or you want a finish that really makes your part shine literally. The cutting edges of face mills are always located along its sides. As such it must always cut in a horizontal direction at a given depth coming from outside the stock.
There are typically two Face mill options: Roughing/hogging and Finishing. Roughing/hogging mills are designed so that the machine geometry, flutes, and materials can be used for rapid and heavy material removal.
Face mill blades cut with the face end of the cutter rather than their sides. The term “face” refers to the creation of a flat face on the work-piece. Multiple teeth distribute the chip load, and since the teeth are normally disposable carbide inserts, this combination allows for very large and efficient face milling operation.