Security
CAPTCHA
Abbreviation for Completely Automated Public Turing test to tell Computers and Humans Apart
In short and in plain language
A CAPTCHA is a test that is meant to tell people apart from automated programs.
It may use letters that are bent out of shape or picture puzzles. It is meant to slow down bots that misuse forms and logins.
Such tests can shut out people with impairments. So other options matter.
Definition
A CAPTCHA is a test intended to tell people apart from automated programs, for example with distorted letters or picture puzzles. It is meant to slow down misuse of forms and logins by bots. Such tests can exclude people with impairments, so alternatives matter.