Cloud service roles comprise a set of application and configuration files. There are 2 kinds of roles provided by Azure:
Web role: This provides a dedicated web server belonging to IIS (Internet Information Services) that is used for automatic deployment and hosting of front-end websites.
Worker role: These roles help the applications hosted within them to run asynchronously for longer durations and are independent of the user interactions and generally do not use IIS. They are also ideal for performing background processes. The applications are run in a standalone manner.