Java 9 is a unique major release for Java. What makes it unique is its introduction of modular components and segments throughout the entire JDK.
This very feature is given the name, ‘Project Jigsaw’.
The primary goals of this Project are to:

• Make the Java SE Platform, and the JDK, more easily scalable down to small computing devices
• Improve the security and maintainability of Java SE Platform Implementations in general, and the JDK in particular
• Enable improved application performance
• Make it easier for developers to construct and maintain libraries and large applications, for both the Java SE and EE Platforms.
• The module system should be powerful enough to modularize the JDK and other large legacy code bases, yet still be approachable by all developers.

Here is a curated list of 2016 JDK9 talks from @Devoxx & @JavaOneConf.