Web role
The web role provides all web endpoints like the web site, the web services and the internal security token service
The web role provides the following web endpoints
ISHCSwhich is the Organize Space web applicationISHWSwhich hosts all web servicesISHSTSwhich is the internal Security Token ServiceISHCMwhich is used for hosting MVC pages and other files for Client Tools synchronization files
Since the Web role is required on every Content Manager installation, an out-of-the-box Content Manager installation will enable all web endpoints.
The Web role is used to serve external clients, but it is also used to serve the internal roles like the Translation role and the Default background task role. When it is used for external web endpoints, the Web role can be scaled out via Network Load Balancing (NLB).