Basic Concepts about the Java Platform 
Java SE Technology - At a Glance , Java Technology for Mobile and Interactive Devices, JavaFX Technology - At a Glance

Java Technology Glossaries
Check out these glossaries of terms related to Java SE, Java EE, and Java ME technologies.

Java SE API & Documentation
These are the APIs that you'll need to use for programming to the Java platform.

Adoption Guide
Use this guide if you are upgrading from a previous version of the JDK.

Unraveling Java Terminology
This article defines the most common Java terminology in easy-to-scan, alphabetical order, and provides links for more information and downloads.

Java SE 7 Platform at a Glance
Use this interactive diagram to find more information about Java SE 7 components.

The Java Language Specification, 3rd Edition
The Java Language Specification, 3rd Edition is the definitive technical reference for the Java programming language.