The CAPTCHA is a security program that only allows humans access and prevents robots action. For example during the registration process of g-mail account you will be asked to solve the captcha(typing the letters from the given image). This process can be easily done by humans, but there is no programs to solve captchas directly. Captcha solving is must when you open e-mail accounts, net banking, for signing up in websites and many more. They use this to save them and their customers from hacking and other scam activities.
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