reCAPTCHA is used to protect websites from spam & abuse. It’s a free service provided by Google which is a turning test to tell humans and bots separately. Humans can solve the given task easily and it’s impossible for bots and other harmful software to figure it out.
To add the reCAPTCHA field into your form, you’ll have to integrate it with reCAPTCHA V2 or reCAPTCHA V3.