Bots are simple software programs that carry out routine tasks on Wikipedia that humans cannot do quickly enough, or not without becoming insanely bored. You can follow their work just as you can a human editor, as each is required to have its own user account.
There are more than 2,000 bots approved for use on Wikipedia. Some more common uses include correcting common typographical errors, reverting obvious vandalism, and alerting editors when something is wrong but requires human intervention to decide what to do next.
Bots were once a little controversial: they took editing tasks away from humans, and a runaway bot could cause a lot of harm rather quickly. So basically, all the same concerns we have about robots and the future of mankind, Wikipedia already hashed out more than a decade ago.
Happily, on Wikipedia, humans and bots have learned how to coexist peacefully.