First there are no methods of the Serializable interface. Seems weird huh. By implementing the serializable interface, if allows the object to be "Serialized", go figure. Much like the Clonable interface, except that no methods need to be overridden. Basically, serializing an object stores the objects class, fields, methods, and data into a byte code text file so that it might be retrieved later. This is done with an ObjectOutputStream and ObjectInputStream
How to use it effectively? People have written whole chapters on that. My advice is to go the Library and check out a Java 2 book.