here's a quick tutorial: http://www.tutorialspoint.com/java/java_serialization.htm

if you want to build two java programs that communicate over a network there is another option: Remote Method Invocation (RMI):  http://docs.oracle.com/javase/tutorial/rmi/index.html

Serialization is more low level. you get a stream of bytes from an object, and you can do with it what you want. e.g. save it to file, send it around,... and later deserialize to get the object back.

RMI is an API for building distributed applications. essentially you can call methods on java objects running on remote computers and it will handle all the network communication for you. RMI uses serialization to do just that.