The Box projection is an extension of XYZ To UVW mapping - the projection of the planes of the cube are based on the normal direction of the surface. Box projection provides a quick way to map a texture on any object without too much distortion. However, the seams between the projection planes of the box may be visible in the render, depending on the shape of the surface (Figure 1).
Figure 1: The result of using Box projection applied to a Checks texture node