A google search of "ear file" brings up 8.8 million hits. I'll bet one of those will answer your question. [ December 08, 2005: Message edited by: Bear Bibeault ]
Now what is the difference b/w Web Application and Enterprise Application?
with the same question make a simple search in servlet forum and scwcd forum. I bet you will end up in really good explanations. Before posting a question try making a search in the forum, and figure out whether it has already been discussed. In that way you save lot of your precious time.