JDK,JRE and JVM.

 JDK - Used for develop the application, its provider the tool kit for develop.Here we write the .java class.It includes the JRE, set of API classes, Java compiler and additional files needed to write Java applications.

JRE - Used for compile the java class. Its convert the java code into byte code, mean .java to .class using java compiler.Its JER contains compiler and APIs.Its contains JVM , Core libraries and other additional components to run applications.

JVM - Used to execute the .java class. To execute the .class file we have interpretor. This interpretor read every line of byte code and execute that.