The Java Runtime Environment, or JRE, is a software bundle from Sun Microsystems that allows a computer system to run a Java application. Java applications are in widespread use and necessary to view many Internet pages. Normal computer users can download the current JRE version by testing their Java Virtual Machine at the Java.com test page.
The software bundle consists of the Java Virtual Machine and the application and programming interface (API). The API provides a set of standard class libraries. The virtual machine and API have to be consistent with each other and are therefore bundled together as the JRE. This can be considered a virtual computer in which the virtual machine is the processor and the API is the user interface.