JVM (Java Virtual Machine) is an abstract machine.It is a specification that provides runtime environment in which java bytecode can be executed. JVMs are available for many hardware and software platforms (i.e. JVM is plateform dependent).
The JVM performs four main tasks:
- Loads code
- Verifies code
- Executes code
- Provides runtime environment
JRE is an acronym for Java Runtime Environment.It is used to provide runtime environment.It is the implementation of JVM.It physically exists.It contains set of libraries + other files that JVM uses at runtime.
JDK is an acronym for Java Development Kit.It physically exists.It contains JRE + development tools.