Comment Validators stop spam from bots.
There are three common types of comment validators; registration validators, comment validator (human check) and ‘Captcha‘.
Captcha is the generally system used, it requires you to input a string of characters based on a displayed image or a short audio clip.
Comment Validator (or human check) requires a simple equation or simple human input to go through the website.
For information on Registration Validators
see Registration Validator