A Bot can be thought of like Siri - the ability to "respond" intelligently to questions and commands you may have. Think of it as Google Search on steroids - instead of just putting in a few keywords, you could type things like "Book me a meeting with Jim Brown at ABC Corp sometime next week." That simple request would initiate a bot, and that bot would act on behalf of you - reviewing your calendar, finding open dates and times, sending the invite with those times to Jim, processing his responses. Finally, after a day or two, the bot would simply reply "Your meeting with Jim Brown at ABC Corp has been scheduled for next Tuesday at 9am. Jim would like you to send him an agenda before the meeting".
Think about that for a moment - the ability of an automated agent to help streamline the mundane, eliminating the "busy work" from your life. Productivity is about to reach a whole new level in businesses in the years to come.