Understanding CAPTCHA and its purpose

CAPTCHA is a contrived acronym for – “Completely Automated Public Turing test to tell Computers and Humans Apart”.
A CAPTCHA is a challenge-response test (most often placed within web forms) to determine whether the user is human or a computer application.

The purpose of CAPTCHA is to BLOCK form submissions from bots. Internet bots/ web robots/ WWW robots or simply bots, are the software applications that run automated tasks over the internet.