JDK or Java Runtime Environment and JRE or Java Development Kit are two software packages used to aid certain functionalities of Java applications. When you understand what the two software packages are used for, you will be able to differentiate the two without any difficulty.
JRE is used majorly for the interpretation of Java application and its execution on the operating system. JRE can do this because it contains applications that allow these functionalities. JDK, on the other hand, is used for the compilation and debugging of Java applications through the help of the tools that comes with it.
This means that with JDK, you can easily create Java applications, whereas JRE only comes with tools and applications that will help you to use the Java applications. In terms of usage, JDK has less platform range compared to JRE. The JDK is used majorly by programmers, while the use of JRE is not limited to the programmers.