What is CAPTCHA - Definition
CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) - is a security test designed to distinguish between human users and visitors. The main job of this web form is to protect against spam and stop automatons (called bots) from entering any data into a website. Bots are programmed to perform specific tasks, meaning that they follow instructions without a human having to run them each time manually. Traditional captchas often mimic or replace the behavior of a human user - and if used viciously, they can have a devastating effect on any website they attack.
Example of CAPTCHA tests
CAPTCHA test hinges on user interaction. Human users will be able to perform an action that automated boot requires to do. Usually, modern captchas can be either image-based captchas or audio captchas. Image recognition captchas are based on identifying objects or random letters—the audio captcha - on audio files that a person needs to transfer to writing text.