What is a WAR file?
A Web archive (WAR) file is a packaged Web application. WAR files can be used to import a Web application into a Web server. The WAR file also includes a Web deployment descriptor file. There are special files and directories within a WAR file. The /WEB-INF directory in the WAR file contains a file named web.xml which defines the structure of the web application. If the web application is only use JSP files, then web.xml file is not strictly necessary. If the web application uses servlets, then the servlet container uses web.xml to ascertain to which servlet a URL request is to be routed.