CAPTCHA, short for “Completely Automated Public Turing test to tell Computers and Humans Apart,” is a security measure used to distinguish between human users and automated bots on the internet. It typically involves presenting users with a challenge, such as distorted letters or images, that they must successfully complete in order to prove their human identity and gain access to a website or online service. This helps prevent spam, fraud, and other malicious activities by ensuring that only real people are interacting with the digital world. CAPTCHAs have become an integral part of online security, providing a simple yet effective way to protect websites and their users from unwanted automated attacks.