JRE JDK JVM JIT

JRE	JDK	JVM	JIT
Java Runtime Environment	Java Development Kit	Java Virtual Machine	Just In Time Compiler
Java Runtime Environment (JRE) is an implementation of the JVM.	JDK is a software development kit (SDK) or program development environment for writing java applets and applications.	JVM becomes an instance of JRE at runtime of a java program.  It is widely known as a runtime interpreter.	JIT is the part of the Java Virtual Machine (JVM).
All browsers including Internet Explorer, Firefox and Chrome can work with JRE to execute java programs.	It consists of runtime environment (JRE) that "sits on top" of the operating system layer.	JVM has an instruction set and manipulates various memory areas at run time.	It is used to improve performance of JVM and speed up the execution time.
JRE is meant for users to execute java programs.	Java Development Kit (JDK) is meant for Programmers, contains various development tools like Java libraries, Java source compilers, Java debuggers, bundling and deployment tools.	Thus for different hardware platforms one has corresponding implementation of JVM available as vendor supplied JREs.	JIT compiles parts of the byte code that have similar functionality at the same time, and hence reduces the amount of time needed for compilation.
JRE are platform specific	Like JRE, JDK are also platform specific	Like JRE JVMs are also platform specific	JIT is part of Java Virtual Machine.

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