What is the difference between JVM and JRE?

A Java Runtime Environment (JRE) is a prerequisite for running Java applications on any computer. A JRE contains a Java Virtual Machine (JVM), all standard, core java classes and run time libraries. It does not contain any development tools such as compiler,debugger, etc. JDK (Java Development Kit) is a whole package required to Java Development which essentially contains JRE+JVM, and tools required to compile and debug, execute Java applications.