Captcha, which stands for Completely Automated Public Turing test to tell Computers and Humans Apart, is a type of challenge-response test used in computing to determine whether or not the user is human. This test is designed to prevent automated software or bots from conducting abusive activities on websites. It typically involves tasks that are easy for humans but difficult for computers, such as recognizing distorted text, identifying objects in images, or solving simple puzzles. By successfully completing a CAPTCHA, a user proves that they are not an automated program, allowing them to proceed with actions such as signing up for a service, posting a comment, or downloading a file. CAPTCHAs are widely used across the internet to enhance security and prevent spam and automated data extraction.