A mapped material is a material that contains one or more maps. Typically, it contains a bitmap as a Diffuse map, but having any map or maps applied qualifies a material as mapped.
In order for a mapped material containing a 2D map to appear properly in the viewports and in the rendered image, any object to which it’s applied generally needs mapping coordinates. By default, most parametric objects in 3ds Max already have mapping coordinates applied; you can also use the UVW Map modifier (link) or Unwrap UVW modifier (link) to provide mapping coordinates.