The Java Runtime Environment (JRE) is a software platform that allows you to run Java programs on your computer. It includes the Java Virtual Machine (JVM), which is the core component that executes Java bytecode, as well as the Java Class Library, which provides a set of APIs and classes for developing Java programs.

The JRE is required to run any Java program, including Java applets that are embedded in web pages. It is also used to run Java web applications that are deployed on a Java-based application server.

To run a Java program, you need to have the JRE installed on your computer. You can download the JRE from the Oracle website or from your operating system’s package manager.

Once the JRE is installed, you can run a Java program by using the java command in the command line. For example, to run a Java class called MyProgram, you can use the following command:

java MyProgram

The JRE also includes a set of tools and utilities that you can use to develop and debug Java programs, such as the java command-line compiler, the javac command-line compiler, and the jdb debugger.

Note: The JRE is different from the Java Development Kit (JDK), which is a software development kit that includes the JRE and additional tools and libraries for developing Java programs. The JDK is typically used by Java developers to build and test Java programs, while the JRE is used to run the programs.