a bot is a software program designed to do a specific task.. some just scroll around trying to find security holes.. some do nothing more than try to register websites to drop messages and links for spam and some just multiply and spread spyware. The sad news is they get better and better at working around our defenses each and every day. It's a never ending battle and gets tougher each and every day.
When you register at a sight and it has a picture of letters and numbers that are hard to make out/read that's one way to TRY and defeat a bot from registering. But unfortunately they are getting around that many times.
Try this link
What Is A Bot (or Zombie)? Internet bot - Wikipedia, the free encyclopedia
Allen