There are many types of bots. Bot type is based on the specific task it was programmed to do and the environment it was designed to operate in.
For instance, there are Internet bots that crawl websites to fetch and analyze data (web crawlers). Bots can also control video game characters to gather resources or fight hostile non-player characters (farm-bots). And of course, there are bots that interact conversationally with human users (chatbots).
Bots are created and controlled by humans so they can be programmed to perform malicious actions and harmful Internet attacks too.