Recall from Chapter 3, Charting the Map Class that OpenLayers supports three separate renderer technologies, WebGL, Canvas, and DOM. When OpenLayers draws the layers in a map, it uses one of these renderers to do the actual work of drawing. The renderer requests data from the layer's source for the area being displayed, and then transforms this into the final map image. For raster layers, images are fetched from a remote server and are composited into a Canvas element (for WebGL and Canvas renderers) or <img> tags (for the DOM render). Vector layers work in the same way, but are only supported by the Canvas renderer at the time this book was written. The renderer asks the layer's source to fetch the data it needs and then applies algorithms for rendering the vector data to the Canvas element. As we mentioned earlier, the vector data is not just an image. It can contain additional information such as the coordinates of the data. This additional information can be used for styling features (which we'll cover in detail in the next chapter) or to provide interactive feedback (as we'll see in an example later in this chapter).