Matt Horn, Technical Writer, Allaire Corp., begins his discussion of deployment descriptors, text- based XML files whose elements describe how to deploy and assemble components into a specific environment. These also contain information about the components that can specify settings not contained in the code of the components themselves, such as initialization parameters and security settings. Part I explains the various types of deployment descriptors found in J2EE- compliant systems and then focuses on the web.xml file, the Web component deployment descriptor.
Understanding the web.xml Deployment Descriptor, Part 1 (Allaire Article)