What is Captcha ?
CAPTCHA stands for Completely Automated Public Turing. Captcha used to tell Computers and Humans Apart. Though there are few type of captcha, Visual Captcha is the most widely used because visual captcha is easy to implemented in screen-involved activity.
Do we need to do that ? What is it used for ?
We need captha to validate make sure that some processes are really executed by human, not by computer / robots. Those special process usually involving form input, such as registration, commenting, and others.
