Minecraft wiki entry for Setting_up_a_server, associated text: JRE stand for Java Runtime Environment. JDK stands for Java Development Kit. JRE is a package tool designed to run Java programs. JDK is a package of tools designed to develop Java programs. The JDK comes with the JRE which comes with the JVM. If you have JDK then you have JRE and JVM. Vanilla Minecraft does not need JDK, but plugins may require it.