What is the definition of modifier in 3DS max?

Answer 1

As the name suggests, it modifies the selected object based on what sort of modifier is used. You can select a box and choose a Flex modifier to make it stretch and grow, a Twist modifier to twist the object, a Ripple modifier to create turbulent ripples on the object or a Displacement modifier to make it look lumpy based on the image used as a displacement map. You can also unwrap the polygon coordinates to create a modified UV map and make a texture that fits to your specifications. Alternatively, you can place a UV Map modifier and specify the box field to force the object to texture as if it were a box.

Modifiers come in many forms and certain modifiers are only available to specific object types, like editable spline, editable patch or editable poly. You may be able to locate and download modifiers online that your version of 3DS Max supports or go online and watch tutorials on how to create interesting transformations with multiple modifiers on a single object.