A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) serves as a security measure designed to differentiate between human users and automated bots. By requiring users to solve challenges, such as identifying distorted text or matching images, CAPTCHA prevents spam and fraudulent activities on websites. This is crucial for safeguarding sensitive information during form submissions and login processes. By reducing the risk of automated attacks, CAPTCHAs enhance website security and protect user data, ensuring a safer and more trustworthy online experience.