Difference between Web Server and Application Server

Application server vs Web server

Web Server:

• Handles only HTTP protocol
• Consists of web container alone (Servlet/JSP)
• Code has take care of security, transaction, database connectivity and messaging

Application Server:

• Handles Multiple protocol
• Contains web container + EJB container
• Application server itself will take care of security, transaction, database connectivity, pooled data connections, data caches, session persistence, messaging and fail over protection

Explained more at
1) http://www.javaworld.com/javaqa/2002-08/01-qa-0823-appvswebserver.html?page=1
2) http://www.serverwatch.com/tutorials/article.php/10825_1355131_1/Web-Servers-vs-App-Servers-Choosing-Between-the-Two.htm

Difference Between JAR, WAR and EAR files

All these JAR, WAR and EAR files can be created using JAR tool.

JAR (Java ARchive) contains

• Library Class files
• Resource files
• Property files

WAR (Web ARchive) contains

• JAR files (lib)
• Java Class files (classes)
• JSP, HTML, JS, CSS and image files
• Deployment Descriptor (web.xml) and other configuration XML files

It is also called as Web Module.

EAR (Enterprise ARchive) contains

• WAR files
• JAR files
• Enterprise Java Beans
• Application Deployment Descriptor (application.xml) and other configuration XML files

EAR contains the complete enterprise application which consists of one or more web modules.

Note: Tomcat deals only with WAR files. If you want to install EAR files, use Apache Geronimo

For more details, refer http://www.javaworld.com/javaworld/jw-01-2008/jw-01-tomcat6.html?page=2