reCAPTCHA by Google is a free service that protects your website from spam and abuse. It's designed to be friendly to humans, much more friendly than image-based CAPTCHA. It uses advanced risk analysis techniques to tell humans and bots apart to protect your website from spam.
There are three types of reCAPTCHA that you can use on your website. You are able to set them all up if desired and use different ones on different forms.
Google reCAPTCHA V3
Google reCAPTCHA V2 Checkbox
The "I'm not a robot" checkbox requires the user to click a checkbox indicating the user is not a robot. This will either pass the user immediately (with No CAPTCHA) or challenge them to validate whether or not they are human.
Google reCAPTCHA V2 Invisible