Java is a programming language used to develop applications whereas J2EE is a computing platform which consists of core java with a powerful set of libraries. Core Java usually refers to Java SE which consists of Java language, JVM and JDK.
Web technology refers to the means by which computers communicate with each other using markup languages and multimedia packages. It gives us a way to interact with hosted information, like websites. Web technology involves the use of hypertext markup language (HTML), Java Script and cascading style sheets (CSS)
Database technologies take information and store, organize, and process it in a way that enables users to easily and intuitively go back and find details they are searching for. Database technologies come in all shapes and sizes, from complex to simple, large to small.