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.
Ignition uses the JSON format to store much of its data internally, including Tags and component properties.