Difference Between JDK and JRE
JDK stands for the Java Developer Kit. JDK includes other Java application development tools including JRE. E.g., the Java compiler (javac) is included only in JDK. In case of Java software developer, he needs to use JDK. If he downloads and installs JDK, he does not need to install JRE since JRE is included within JDK.
JRE stands for the Java Runtime Environment. JRE is required to run Java applications. An implementation of the Java Virtual Machine (JVM) is bundled within JRE. If you want to run Java software, you may simply use JRE. The JRE installation file size is also smaller.