The Java Development Kit (JDK) is a software development kit that includes the Java Runtime Environment (JRE) and additional tools and libraries for developing Java programs. It is used by Java developers to build and test Java programs.

The 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.

There are a few key differences between the JDK and the JRE:

• Tools and libraries: The JDK includes additional tools and libraries for developing Java programs, such as the java and javac command-line compilers, the jdb debugger, and the jar archiver. The JRE does not include these tools and libraries.
• Development vs. runtime: The JDK is intended for development purposes, while the JRE is intended for runtime purposes. The JDK is typically used to build and test Java programs, while the JRE is used to run the programs.
• Size: The JDK is generally larger than the JRE, as it includes additional tools and libraries for development.

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

Note: In Java 9 and later, the JDK and the JRE are bundled together in a single package called the Java Platform, Standard Edition (Java SE). This means that you can use the JDK to run Java programs as well as to develop them. However, the JDK and the JRE are still conceptually distinct, and the JDK includes additional tools and libraries that are not included in the JRE.