Tutorial 3dsMax -- Extrude and FaceExtrude modifier
The Extrude modifier adds depth to a shape object and makes it a parametric object. and the Face Extrude modifier extrudes faces along their normals, creating new faces along the sides of the extrusion that connect the extruded faces to their object.
As with most modifiers, this affects the current face selection passed up the stack. There are various differences between the Face Extrude modifier and the Face Extrude function in an editable mesh, especially the fact that all parameters in the Face Extrude modifier are animatable.
Sometimes completely unknown, the modifiers are very useful during the normal workflow of 3dsMax. These are old videos created with 3dsMax2010 but the modifiers are equal to the latest versions