The Full Form of JRE is Java Runtime Environment.

The Java Runtime Environment, or JRE, is a software layer that runs on top of a computer’s operating system software and provides the class libraries and other resources that a specific Java program needs to run.

The JRE is one of three interrelated components for developing and running Java programs. The other two components are as follows:

• The Java Development Kit, or JDK, is a set of tools for developing Java applications. Developers choose JDKs by Java version and by package or edition—Java Enterprise Edition (Java EE), Java Special Edition (Java SE), or Java Mobile Edition (Java ME). Every JDK always includes a compatible JRE, because running a Java program is part of the process of developing a Java program.
• The Java Virtual Machine, or JVM, executes live Java applications. Every JRE includes a default JRE, but developers are free to choose another that meets the specific resource needs of their applications.

The JRE combines Java code created using the JDK with the necessary libraries required to run it on a JVM and then creates an instance of the JVM that executes the resulting program. JVMs are available for multiple operating systems, and programs created with the JRE will run on all of them. In this way, the Java Runtime Environment is what enables a Java program to run in any operating system without modification.

Java is a class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let application developers write once, run anywhere, meaning that compiled Java code can run on all platforms that support Java without the need for recompilation.