Java Development Kit (JDK) is the most widely used Java Software Development Kit. Java Runtime Environment (JRE) is an implementation of the Java Virtual Machine which executes Java programs.

In Java development, JDK (Java Development Kit) and JRE (Java Runtime Environment) are two essential components, and they serve distinct purposes:

JDK (Java Development Kit):
- Definition: The JDK is a software development kit that provides tools needed for developing Java applications.
- Components: It includes the JRE, an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (Javadoc), and other development tools needed for Java programming.
- Use: Developers typically need the JDK to write, compile, and debug Java applications. It’s essential for creating Java applications from scratch.
JRE (Java Runtime Environment):
- Definition: The JRE is an environment that provides the runtime support for Java applications. It includes the Java Virtual Machine (JVM), class libraries, and other runtime components.
- Components: It includes the JVM, libraries, and other files necessary for running Java applications, but it does not contain the tools and utilities needed for Java development.
- Use: End-users who only need to run Java applications (not develop them) require the JRE. It allows the execution of Java programs on a user’s machine.

In summary, the JDK is for Java development, providing tools and utilities for creating, compiling, and debugging applications. The JRE, on the other hand, is for end-users who just need to run Java applications and don’t require development tools.