While the combined build creates a single JavaScript file that contains both OpenLayers library code and your application code, a separate build creates a single JavaScript file that contains just the OpenLayers code required by your application. The main difference with this approach is that we will not use goog.require to tell the compiler what parts of OpenLayers we want to use. Instead, we will use the exports property of the configuration file. The other difference, is that we will not include our application source file in the src configuration.