When a data is submitted to your website, is it by someone typing it out, or is it being submitted by a script? CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. Along with the form that they have to fill out, visitors to your site will be presented with a small task that can only be carried out by someone looking at the screen. An example of this would be to type out some text contained in an image.