Although Machine Learning algorithms have been around since mid-20th century, this technology along with Deep Learning is the newest popular boy in town, with good reason. Due to recent advances in computing power and data availability, they're being more and more used to perform astonishing tasks.
Chatfuel is one of the major chatbot development platforms with thousands of bots published and working. Their success cannot be discussed, however for nonspecialized users, is hard to achieve the development of a fully conversational bot. Why? Because it takes too much time to come up and tag manually all the sentences the bot must understand.