It is essential to master the notion of module in GWT. On the same principle as a JAR file in the Java world, a module is a primary configuration element in GWT.
Contrary to a popular belief, a module is not necessarily an Eclipse project, nor necessarily a JAR file. A module is identified by the fully qualified name of the package in which it is found, associated with the module name.
There can be several modules per Eclipse project, but also several modules per JAR archive. As an example, the gwt-user.jar file constituting the basic GWT framework itself contains more than twenty modules.
Now that the notion of module has been discussed, let’s see the structure of a GWT project as created by the WebAppCreator tool.