WAR stands for Web application Archive. WAR is a compressed file format like the ZIP file which includes jsp, servlet, jar and static web resources etc in a specific hierarchical directory structure called WEB-INF. It is like jar file but follow a specific hierarchical directory structure. WAR files are deployed to the application server like Tomcat or Java EE server like JBoss etc. Here is the list of all WAR tutorial:

How to create war file in eclipse?
How to create war file using ant?