how the Servlet Container Works

Creating a request object and populate it with information that may be used by the invoked servlet, such as parameters, headers, cookies, query string, URI, etc. A request object is an instance of the javax.servlet.ServletRequest interface or the javax.servlet.http.ServletRequest interface.

Creating a response object that the invoked servlet uses to send the response to the web client. A response object is an instance of the javax.servlet.ServletResponse interface or the javax.servlet.http.ServletResponse interface.

Invoking the service method of the servlet, passing the request and response objects. Here the servlet reads the values from the request object and writes to the response object.