Additional software that allows to use interactive applications
Java Runtime Environment (JRE) is a component required for different applications. This component is in fact a library that contains programming code which allows other applications to run.
JRE it is like an operating system for some applications, without this library you cannot use those apps because they are made using Java programming language. In general, this library is used by multimedia or interactive applications.
Usually, programs with great usability are made using Java, but also computer games or interfaces that require drag&drop functionality are made using this technique.