Images in games are called textures. Textures allow us to use real world images to paint our world. Think about what it would take to create a dirt road. You could either color the triangles in exactly the right way to make the overall scene look like dirt, or you could apply an actual image (that is, a texture) of dirt to the triangles. Which of these do you think would look more realistic?
Using textures to fill the triangles
Let's say that you are going to paint your bedroom. You can either use paint to color the walls, or you could buy some wallpaper and put that on your walls. Using images to add color to our triangles is pretty much like using wallpaper to color our bedroom walls. The image is applied to the triangle, ...