:: About Using Captcha ::
Essentially Captcha allows us to prevent bots from posting unwanted messages containing undesirable content or links to sites with undesirable content to our message board. Here's a quick detailed Wikipedia description.

A CAPTCHA or Captcha is a type of challenge-response test used in computing to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen. More about Captcha