An .ear file is an enterprise archive file and is associated with application assembly.
http://java.sun.com/j2ee/j2ee-1_4-pfd-spec.pdf (search for .ear)
To quote:
"The Application Assembler takes a set of components developed by Application
Component Providers and assembles them into a complete
J2EE application
delivered in the form of an Enterprise Archive (.ear) file. The Application
Assembler will generally use GUI tools provided by either a Platform Provider or
Tool Provider. The Application Assembler is responsible for providing assembly
instructions describing external dependencies of the application that the Deployer
must resolve in the deployment process."
A .war files is a web archive file.
This is used for deployment, e.g. you create a war file into which you place your
jsp,
servlets, beans, images, etc.
You then deploy that to tomcat/jrun/websphere and they create an application from that war