A war file is just a jar file (like a zip archive) with a standard structure.

Basic structure:

WEB-INF/ - directory for application support
   lib/ - supporting jar files
   web.xml - configuration file for the application
...

'WEB-INF' is used to package:

• Configuration

• Supporting compiled java code.

• Other non-public information.

The 'web.xml' file tells the J2EE container (Tomcat) what to do.

Everything outside of 'WEB-INF' is public content available via the web server (Tomcat).