Used by marketers to script sequnces of messages, very similar to an Autoresponder sequence. Such sequences can be triggered by user opt-in or the use of keywords within user interactions. After a trigger occurs a sequnce of messages is delivered until the next anticipated user response. Each user response is used in the decision tree to help the chat bot navigate the response sequnces to deliver the correct response message.
Messenger Bots are created using the new Messenger API that allows a bot to send and receive messages. The Messenger Bots are essentially chat bots that you can talk to from the Messenger app. The conversations will of course be different than those you have with your Facebook friends. These bots are meant to help you get information for example you can ask the CNN bot to tell you give you the current headline news and it will fetch them for you.