Technically, the term "JVM" specifies the
Java Virtual Machine. I.e., the "JVM" is the definition of the abstract, stack-based computational engine used to execute Java bytecodes. The term "JRE" stands for the Java Runtime Environment (if you follow Sun's nomeclature) or, interchangeably, Java Runtime Engine. I.e., a JRE is a specific implementation of the the JVM, including the core libaries.