An application server is technology where developers can create, test, and execute application components. Application servers are typically J2EE-based, running EJBs or other Java components. Application servers are designed to create true applications with complex business logic, and have scalability features such as load balancing, fail-over, and process distribution. In other words, it's primarily a development environment. In contrast, Web servers are technology designed to create and deploy Web site, serving up content more so than applications. They both use Web interfaces, but Web servers are more about the interface than the back-end logic. In other words, Web servers serve up content. As time moves on Web servers are looking more like application server, as they adopt their functionality. I can understand the confusion.