A template is a picture file that show how the shape of the 3D object has been mapped to 2D. You can paint over the template in a paint program (Photoshop, Paint Shop, the Gimp, etc.) and make a new material for your object. To use the material, you'd import the new picture you created into the material (or materials) for the object that use that template. Several different material zones on the same object may use the same template image. Some items use multiple templates, because the surface is so complex.