What is JRE?

Java runtime environment : A subset of the Java Developer Kit for end-users and developers who want to redistribute the runtime environment. The Java runtime environment consists of the Java virtual machine, the Java core classes, and supporting files.

The Java Runtime Environment (JRE) :is the minimum standard Java platform for running applications written in the Java programming language. It contains the Java virtual machine, Java core classes, and supporting files. The JRE does not contain any of the development tools (such as appletviewer or javac) or classes that pertain only to a development environment. The JRE for Win 32 platforms is bundled with its own installer program. The availability of an easily installable JRE adds flexibility to the ways in which software suppliers can deliver software to their customers. Vendors of applications have the option of not bundling a copy of the JRE with their software. End-users can download and install the Windows JRE themselves. Once a user has installed the JRE, it can be used to run any number of applications written in the Java programming language.
Java Runtime Environment. A subset of the Java Development Kit required to run Java programs. The JRE consists of the Java Virtual Machine, the Java platform core classes and supporting files. It does not include the compiler or debugger.