The Java Runtime Environment (JRE) is a software package that provides the necessary components to run Java applications. It includes the Java Virtual Machine (JVM), core libraries, and other files that support the execution of Java programs. The JRE allows developers to create applications that can run on any device with a compatible JRE installed, promoting the "write once, run anywhere" philosophy of Java. The JRE is part of the larger Java Development Kit (JDK), which includes tools for developing Java applications. While the JDK is used for creating and compiling Java programs, the JRE is specifically designed for running them. Users typically install the JRE to ensure they can execute Java-based applications on their systems.