The JVM (Java Virtual Machine) is an abstract machine that provides a runtime environment in which Java bytecode can be executed. It follows the "Write Once, Run Anywhere" principle by translating bytecode into machine-specific instructions.

1. Class Loader: Loads, links, and initializes class files.
2. Runtime Data Areas: Memory area used by JVM during program execution.
   • Method Area: Stores class structures, metadata, and static variables.
   • Heap Area: Primary area for object allocation; managed by Garbage Collector.
   • Stack Area: Stores local variables and partial results for each thread.
   • PC Registers: Stores the address of the current execution instruction.
   • Native Method Stack: Used for native methods (written in C/C++).
3. Execution Engine: Executes the bytecode.
   • Interpreter: Reads bytecode and executes instructions sequentially.
   • JIT Compiler: Compiles frequently used code sections into native machine code for better performance.
   • Garbage Collector (GC): Automatically deallocates memory for objects that are no longer reachable.

• Stack: Thread-safe, fixed size, stores primitives and object references.
• Heap: Shared across threads, dynamic size, stores actual objects.

• Memory Leaks: Thinking Java doesn't have memory leaks (e.g., static references holding onto large objects).
• StackOverflowError: Excessive recursion without a base case.
• OutOfMemoryError: Creating too many objects that exceed the heap size.