Java is an object-oriented computer programming language. James Gosling created it in 1995 at Sun Corporation. Java can be used to create several different types of programs such as applets, applications, servlets and JSP. Applications are standalone programs. Applets are similar to applications, but they require another application to run in such as a web browser. Applets adhere to a set of conventions that let them run in a Java-compatible web browser. A web server processes Servlets and JSP.
Java is compiled into byte code. The complied object cannot be processed by the operating system alone. It relies on the Java Virtual Machine (JVM) to process the byte code. This allows compiled Java programs, known as a class, to run on different platforms without be recompiled.