Java is a cross-platform development platform used by many applications. If you want to run Java based applications, you must install a runtime. Java is developed by Oracle. There are two packages: JDK (Java Development Kit) and JRE (Java Runtime Environment). While the first is needed to develop Java applications, for running them you need the runtime.
Due to licensing, on Linux you have the possibility to install only OpenJDK from software repositories. That is an open source GPL licensed JDK edition. Well, I had this one installed (package openjdk-8-jre) on Ubuntu and I was facing some problems. JabRef, a references manager application, wouldn't run. Initially I thought there is something wrong with the current release. Later I installed (the GUI installer worked) STM32CubeProgrammer, a programming utility for STM32 microcontrollers. Neither this one would launch.
Java Runtime Download page for Linux
