A reference or Reference Type in Java will is based on a class rather than on one of the primitive types. This class could be written by yourself or already exists in Java. Like in the following example, you are creating a reference to the class. Where ObjectClass is a real class somewhere in your packages.

ObjectClass objectName = null;

This is not yet an object. By writing the following line:

ObjectClass objectName = new ObjectClass();

do you create an object/instance. Therefore, it was just a reference to the class.