A bot is a computer program designed to perform tasks automatically, without a human controlling it every time. The word is short for “robot,” but bots exist as software rather than physical machines.

Some bots are helpful: search engines use bots to scan millions of websites and organize information so you can find what you need. Video games often include bots that play as computer-controlled opponents when you don't have other people to play against. Customer service bots can answer simple questions on websites, like “What are your store hours?”

Other bots cause problems. Spam bots flood websites with unwanted advertisements or fake comments. Some bots try to cheat in online games by playing perfectly, ruining the fun for real players. Social media bots sometimes pretend to be real people, posting fake content or spreading misinformation.

When someone accuses another person of being a bot online, they usually mean the person is acting mechanical or fake, posting repetitive messages, or seeming suspiciously inhuman. The challenge with bots today is that sophisticated ones can be hard to distinguish from real people, which is why many websites now use CAPTCHA tests (those puzzles asking you to identify traffic lights or type distorted letters) to verify that a real human is using the site.