JDK or the Java Development Kit is a set of a Java compiler,
a Java interpreter, developer tools, Java API libraries,
documentation which can be used by Java developers to
develop Java-based applications.

JRE or the Java Runtime Environment is a minimum set that
includes a Java interpreter, Java API libraries, Java
browser plug-in, which make up the minimum environment to
execute Java-based applications.

The JVM or Java Virtual Machine is the core of the Java
platform and is a part of both the JDK and JRE that
translates Java bytecodes and executes them as native code
on the client machine.

JDK includes a JRE as as subset.

JDK is a software bundle consists of binary files such as
(javac,java,javadoc,jdb,javap,rmic....),java library files 
(both old and new)and some header files. Development 
environment requires this software.

JRE is also a software bundle same as JDK excluded with 
some binary files( especially compiler - javac and 
rmic ).Required to run applications of production 
environment ( on client host system ).

JVM is available in both JDK and JRE. Java.exe file is used 
to initiate VM process.The default heap size is 2MB and the 
Max.heap size is 64MB.VM comes in two flavours...

-Hotspot client VM
-Hotspot server VM

JDK: Java Developer Kit contains tools needed to develop 
the Java programs, and JRE to run the programs. The tools 
include compiler (javac.exe), Java application launcher 
(java.exe), Appletviewer, etc…

Compiler converts java code into byte code. Java 
application launcher opens a JRE, loads the class, and 
invokes its main method.

You need JDK, if at all you want to write your own 
programs, and to compile them. For running java programs, 
JRE is sufficient.

JRE: Java Runtime Environment contains JVM, class 
libraries, and other supporting files. Actually JVM runs 
the program, and it uses the class libraries, and other 
supporting files provided in JRE. If you want to run any 
java program, you need to have JRE installed in the system.

JVM: Java Virtual Machine interprets the bytecode into the 
machine code depending upon the underlying operating system 
and hardware combination. It is responsible for all the 
things like garbage collection, array bounds checking, etc… 
JVM is platform dependent.

The JVM is called "virtual" because it provides a machine 
interface that does not depend on the underlying operating 
system and machine hardware architecture. This independence 
from hardware and operating system is a cornerstone of the 
write-once run-anywhere value of Java programs.

JDK is the java development kit contains the executable 
files
JRE is the java run time envirnment contains all the 
runtime jar files
JVM is the java virtual machine which is used to convert 
the byte code to user understandable code

JDK- JDK stands for java development kit which contain jre
and jvm and other supporting tools for development of programs.

JRE- JRE stands for java runtime environment which provide
the neccesory jar file that compile source code into byte
code. and it contain java virtual machine .

JVM- JVM stands for java virtual machine that convert byte
code into native code . the native code are those code that
are understandable by machine.