This Post is about to have a quick view on how the SharePoint Servers Communicate with each other, it starts with
When a user issues a query, the query is sent to a Web server. The Web server communicates with the query server to build a list of results, and then communicates with the computer running Microsoft SQL Server to extend the list of results with summarization text, URLs, and security trimming. In parallel, the Web Server gets page data from SQL Server and renders them on fly. This diagram will help in understanding which roles to use on farm servers.