This learning trail is focused on Java SE applications. A Java SE application is an application written to the Java Platform, Standard Edition (Java SE). The same unmodified Java SE applications can be run on almost any computer, whether that computer uses the Microsoft Windows, Solaris, Linux, or OS X operating systems. The key to this application portability is the Java Runtime Environment, which is available free of charge for most operating systems, including all of the ones mentioned above.

In addition to being a platform for multi-platform desktop applications, the Java SE platform is the basis for other technologies such as Java Platform, Enterprise Edition. You might find yourself writing Java code that provides back-end server logic for web and enterprise applications as well.