A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a security measure used to confirm that a user is human rather than a bot. It requires users to complete tasks that are easy for humans, such as identifying objects in images or solving simple puzzles, but challenging for automated systems. CAPTCHAs are commonly implemented on websites to prevent spam, ensure form submissions are genuine, and protect against various types of cyber attacks. Bybarriers, they enhance online security and data integrity.