编译代码和将Java代码转换为字节码需要JDK，而执行字节码需要jre。

如果你是一个Java程序员，你的系统中需要JDK，这个包将包括JRE和JVM，但如果你是一个喜欢玩在线游戏的普通用户，那么你只需要JRE，这个包中没有JDK。

JVM JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed. JVMs are available for many hardware and software platforms. JVM, JRE and JDK are platform dependent because configuration of each OS differs. But, Java is platform independent. JRE It contains everything you need to run Java applications in compiled form. You don't need any libraries and other stuffs. All things you need are compiled. JRE is can not used for development, only used for run the applications. Java SE Development Kit (JDK) The JDK includes the JRE plus command-line development tools such as compilers and debuggers that are necessary or useful for developing applets and applications.

(来源:GeeksForGeeks Q&A, Java平台概述)

JVM (Java虚拟机)是一种抽象机器。它是一个提供运行时环境的规范，在该环境中可以执行java字节码。

JRE是Java运行时环境的首字母缩写。它用于提供运行时环境。它是JVM的实现。它是物理存在的。它包含一组库+ JVM在运行时使用的其他文件

JDK是Java Development Kit的首字母缩写。它是物理存在的。它包含JRE +开发工具

通俗地说:JDK是祖父，JRE是父亲，JVM是他们的儿子。 [即JDK > JRE > JVM]

JDK = JRE +开发/调试工具 JRE = JVM + Java包类(如util, math, lang, awt,swing等)+运行时库。 JVM =类装入器系统+运行时数据区+执行引擎。

换句话说，如果你是一个Java程序员，你将需要JDK在你的系统中，这个包将包括JRE和JVM，但如果你是一个喜欢玩在线游戏的普通用户，那么你只需要JRE，这个包不会有JDK。

JVM:

The Java Virtual Machine (JVM) is the virtual machine that run the Java bytecodes. The JVM doesn't understand Java source code, that's why you compile your *.java files to obtain *.class files that contain the bytecodes understandable by the JVM. It's also the entity that allows Java to be a "portable language" (write once, run anywhere). Indeed there are specific implementations of the JVM for different systems (Windows, Linux, MacOS, see the wikipedia list..), the aim is that with the same bytecodes they all give the same results.

JDK和JRE

要解释JDK和JRE之间的区别，最好是阅读Oracle文档并参考图:

Java运行环境(JRE)

The Java Runtime Environment (JRE) provides the libraries, the Java Virtual Machine, and other components to run applets and applications written in the Java programming language. In addition, two key deployment technologies are part of the JRE: Java Plug-in, which enables applets to run in popular browsers; and Java Web Start, which deploys standalone applications over a network. It is also the foundation for the technologies in the Java 2 Platform, Enterprise Edition (J2EE) for enterprise software development and deployment. The JRE does not contain tools and utilities such as compilers or debuggers for developing applets and applications.

Java开发工具包(JDK)

JDK是JRE的超集，包含JRE中的所有内容，以及开发小程序和应用程序所需的编译器和调试器等工具。

注意，Oracle并不是唯一提供JDK的公司。

JIT编译过程(来源:Oracle文档)

上面的答案(Pablo)是非常正确的。这只是额外的信息。

顾名思义，JRE是一个环境。它基本上是一堆包含java相关文件的目录，即:

bin/ contains Java's executable programs. The most important is java (and for Windows, javaw as well), which launches the JVM. There are some other utilities here as well, such as keytool and policytool. conf/ holds user-editable configuration files for Java experts to play with. lib/ has a large number of supporting files: some .jars, configuration files, property files, fonts, translations, certs, etc. – all the "trimmings" of Java. The most important is modules, a file that contains the .class files of the Java standard library. At a certain level, the Java standard library needs to call into native code. For this purpose, the JRE contains some .dll (Windows) or .dylib (macOS) or .so (Linux) files under bin/ or lib/ with supporting, system-specific native binary code.

JDK也是一组目录。它是JRE的超集，增加了一些功能:

Bin /已经被开发工具放大了。其中最重要的是javac;其他包括jar、javadoc和jshell。 添加了jmods/，用于保存标准库的JMOD文件。这些文件允许标准库与jlink一起使用。

JDK包括JRE和命令行开发工具，如编译器和调试器，这对于开发applet和应用程序是必要的或有用的。

JRE基本上是运行Java程序的Java虚拟机。它还包括用于Applet执行的浏览器插件。

JDK是一个抽象机器。它是一个提供运行时环境的规范，在该环境中可以执行java字节码。

所以，基本上JVM < JRE < JDK就像@Jaimin Patel说的那样。