Open domain chatbots tends to talk about general topics and give appropriate responses. In other words, the knowledge domain is receptive to a wider pool of knowledge. However, these bots are difficult to perfect because language is so versatile. Conversations on social media sites such as Twitter and Reddit are typically considered open domain — they can go in virtually any direction. Furthermore, the whole context around a query requires common sense to understand many new topics properly, which is even harder for computers to grasp.
A bot is software that is designed to automate the kinds of tasks you would usually do on your own, like making a dinner reservation, adding an appointment to your calendar or fetching and displaying information. The increasingly common form of bots, chatbots, simulate conversation. They often live inside messaging apps — or are at least designed to look that way — and it should feel like you’re chatting back and forth as you would with a human.

[In] artificial intelligence ... machines are made to behave in wondrous ways, often sufficient to dazzle even the most experienced observer. But once a particular program is unmasked, once its inner workings are explained ... its magic crumbles away; it stands revealed as a mere collection of procedures ... The observer says to himself "I could have written that". With that thought he moves the program in question from the shelf marked "intelligent", to that reserved for curios ... The object of this paper is to cause just such a re-evaluation of the program about to be "explained". Few programs ever needed it more.[8]