Objects can respond differently to the same message.
Both waiter as kitchen respond to 'a black coffee'.
The actions are different though.
The same message with different implementations, that is polymorphism.
- The waiter passes the message to the kitchen, waits for response, delivers coffee and settles the account.
- The kitchen brews fresh coffee and passes it to the waiter.
Polymorphism makes Object Oriented systems extremely suitable for various exceptions and exceptions to exceptions.