What is the difference between JDK, JRE, and JVM?

These three acronyms represent different levels of the Java ecosystem. The JVM (Java Virtual Machine) is the runtime engine that executes Java bytecode — it handles memory management, garbage collection, and translates bytecode to machine code for the host OS. The JRE (Java Runtime Environment) is the JVM plus the standard class libraries needed to run Java programs — end users need the JRE to run Java applications. The JDK (Java Development Kit) is the complete development package: JRE plus the compiler (javac), debugger, and other tools needed to write and compile Java programs. Developers need the JDK; end users only need the JRE.