Is the JVM a compiler or an interpreter?

First, let's have a clear idea of the following terms
Javac is Java Compiler -- Compiles your Java code into Bytecode
JVM is Java Virtual Machine -- Runs/ Interprets/ translates Bytecode into Native Machine Code
JIT is Just In Time Compiler -- Compiles the given bytecode instruction sequence to machine code at run-time before executing it natively. It's main purpose is to do heavy optimizations in performance.
So now, Let's find answers to your questions..
1)JVM: is it a compiler or an interpreter? -- Ans: Interpreter
2)what about JIT compiler that exist inside the JVM? -- Ans: If you read this reply completely, you probably know it now
3)what exactly is the JVM? -- Ans:
  • JVM is a virtual platform that resides on your RAM
  • Its component, Class loader loads the .class file into the RAM
  • The Byte code Verifier component in JVM checks if there are any access restriction violations in your code. (This is one of the principle reasons why java is secure)
  • Next, the Execution Engine component converts the Bytecode into executable machine code

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