According to the official documentation, JavaFX Observable is an entity that wraps content and allows to observe the content for invalidations.
You can make use JavaFX observable in normal java applications too, you just have to make sure that the JavaFX runtime is available in your classpath.
This video explains the basics as well as real world use cases of JavaFX observable properties. Observables allows JavaFX Binding which allows to define a strict relationship between variables. JavaFX provides a set of predefined observable classes for using this feature directly out of the box.
Some of the ready-to-use observable implementations are given below.
SimpleBooleanProperty
SimpleDoubleProperty
SimpleFloatProperty
SimpleIntegerProperty
SimpleListProperty
SimpleLongProperty
SimpleMapProperty
SimpleObjectProperty
SimpleSetProperty
SimpleStringProperty
SimpleStyleableBooleanProperty
SimpleStyleableDoubleProperty
SimpleStyleableFloatProperty
SimpleStyleableIntegerProperty
SimpleStyleableLongProperty
SimpleStyleableObjectProperty
SimpleStyleableStringProperty
JavaFX ObservableList tutorial:
Code is available in GitHub: https://github.com/afsalashyana/JavaFX-Tutorial-Codes/tree/master/JavaFX%20Observable