At present there is a lot of attention on Conversational User Interfaces, Bots, and ChatBots – especially interesting/exciting for those who are interested (design and build) in how people interact with computers.
To reduce ambiguity it’s worth distinguishing between ‘Chat’ and ‘Bot’. Here I consider Chat as the interaction model whose interface is predominantly through natural conversation, the medium is the Conversational User Interface (Conversational UI or CUI for short).
A Bot is a agent (software application/service) that can carry out a task (semi-)autonomously on behalf of the user. Therefore the ChatBot is an Bot who interfaces with the user via conversation but achieves some task autonomously.