If you are new to SAP Web AS Java, these are the familiar terms that being used.
Java is an object-oriented and platform-independent programming language that has spread across many areas.
Java Runtime Environment is an independent platform environment to run Java program
Java Programs consist of application and applet. Java applications are computer programs with the full functional range also provided by other programming languages. The term applet essentially means “little application”. It usually means a Java applet, a small computer program that runs in a Web browser and is written in the Java programming language.
Java virtual machine is a model of a processor (which often does not exist as real hardware) and the associated system architecture. It is a computer program that emulates a processor. see graphic below.
A Java Development Kit (JDK) is required to write platform-independent Java programs. The Java Development Kit includes the software required to create and test Java applications and applets, the packages with the Java classes that are part of the basic configuration, and the online documentation
Java Standard Edition (Java SE). The standard edition is the normal software environment and defines the Java™ SE Development Kit (JDK). This includes the Java SE Runtime Environment (JRE).
Java Enterprise Edition (Java EE). The enterprise edition builds on the JDK and integrates additional packages such as Enterprise JavaBeans (EJB), servlets, JavaServer Pages (JSP), Java Mail API, and Java Transaction Service (JTS). The Java EE SDK (Software Development Kit) includes the Sun Java System Application Server and requires a JDK.
Java Micro Edition (Java ME). The micro edition is a small runtime environment for small devices such as Personal Digital Assistants (PDAs) or telephones.
Enterprise Java Beans is a package of application logic components in accordance with Java EE specification.
EJB Container is a location to execute Enterprise Java Beans which is part of Java EE application server.
Web Container is a part of Java EE Application Server which Java Server Pages and Java servlets are executed in.
Java Server Pages (JSP) are a technology developed by Sun, which essentially allow the simple dynamic generation of HTML and XML output for a Web server.