What is the difference between an Azure Web Role and Azure Worker Role
The main difference between a Web Role and an Azure Worker Role is that a Web Role supports and runs Internet Information Services (IIS), while an instance of a Worker Role does not. Because information is being deployed and delivered through Azure Service Platform, both can be managed in the same way and can be deployed on a similar Azure Instance. In most scenarios, Web Role and Worker Role instance work together and are often used by an application simultaneously.
For example, a web role instance might accept requests from users, then pass them to a worker role instance for processing.