Message Oriented protocols send data in distinct chunks or groups. The receiver of data can determine where one message ends and another begins. Stream protocols send a continuous flow of data.
Here is an example with mobile phones. Text messages would be a message oriented protocol as each text message is distinct from the other messages. A phone call is stream oriented as there is a continuous flow of audio throughout the call.
Common protocols used on the internet are UDP (message oriented) and TCP (stream oriented). Wikipedia these terms for more information.
Hope this helps