The JVM (Java Virtual Machine) is a run-time engine that allows Java APPLICATIONS to run. The JVM is the program that executes the main method in java programming. JVM is a component of JRE (Java Runtime Environment).

WORA refers to Java programmes (Write Once Run Anywhere). This means that a PROGRAMMER can write Java code on one SYSTEM and expect it to operate without modification on any other Java-enabled device. All of this is feasible because of JVM.

When we compile a .java file, the Java compiler creates .class files (byte-code files) with the same class NAMES as the .java file. When we run this.class file, it goes through a series of phases. These steps sum up the JVM as a whole.

The execution engine scans the byte-code line by line, extracts data and information from various memory areas, and then executes the instructions. The Java NATIVE Interface (JNI) is a user interface that interacts with Native Method Libraries and provides native libraries (C, C++) for execution. It allows JVM to call C/C++ libraries and be called by C/C++ libraries that are hardware-specific. Native Method Libraries are a set of Native Libraries (C, C++) that the Execution Engine requires.