Servlets and JSP (JavaServer Pages) are the main way that Java is used in the Web today. These are Java programs that run on a Web server that allow HTML content to be dynamically generated (often by querying a database) and then sent via the web to a "client" machine that made the request in the first place. Jorelid's book concentrates on teaching the programmer how to fit the various pieces together spending as little time as possible on plumbing.