A software language and platform developed by Sun Microsystems. Ignition is written using the Java language. In order to run a program written in Java, you must have the JRE (Java Runtime Environment) installed on your computer. There are versions of the JRE for pretty much every conceivable operating system, which makes programs written in Java very portable. Because of this, Ignition can be installed on Windows, OSX, and Linux operating systems.
Scripting in Ignition does not use Java, instead it uses the Jython language. This means you script with Python, but have access to some parts of Java.
The Java Database Connectivity (JDBC) API gives Java access to many databases. Many JDBC Drivers have already been written, and can be loaded directly into Ignition to allow connections to a number of databases. Ignition comes with many big drivers already installed, ie: MySQL Microsoft SQL Server, Oracle, etc.
The Java Virtual Machine (JVM) is an abstraction layer between a Java application and the underlying platform. As the name implies, the JVM acts as a “virtual” machine or processor. To the bytecodes comprising the program, they are communicating with a physical machine; however, they are actually interacting with the JVM. -techopida
When we talk about "the JVM" in Ignition, we are referring to the underlying layer of code that is running everything.
Jython is the scripting language Ignition uses in the Designer. Jython (Java-Python) can be used in an event based system like Ignition and uses the Python functions and syntax, but allows users access to Java methods.
You can find out more about Jython here.
You can find out more about the usable functions in Python here.