Heterogeneous means many layer of materials sandwiched together to create the flooring material.  You will see wood looks as the most common form of this type of material but you can get many different effects such as stones or textile appearances.  The technology includes a stabilizing base layer on the bottom of the material (this is also formulated for adhesion) or in some products a cushion layer, and then a picture of whatever the floor is designed to resemble followed a top coat or wear layer.  Can be sheet, plank or tile but the title Heterogeneous usually refers to a sheet product.  It is often called LVT or Luxury Vinyl Tile or LVP Luxury Vinyl Plank in a non-sheet format.