CAPTCHA will demonstrate information about word tests for easy human recognition. CAPTCHA used to differentiate human and non -human or bots.Gibbs resampling repeatedly generate random word until the word becomes human-readable. Passwords are commonly used for authentication purpose. Two types of attacks are Brute Force attack and Dictionary Attack. Those attacks can be avoided using CAPTCHA. Bots using Optical Character Recognition (OCR) program for tracing CAPTCHAs.