(1) reCAPTCHA: reCAPTCHA is a free anti-spam service of Google that protects your website from spam and abuse. Once you register your website for Google reCAPTCHA, you will get a site and secret key. So, to activate the reCAPTCHA, you need to set both site and secret keys. Select a reCAPTCH version. Both versions (v2 and v3) are supported by the Real Testimonials Pro plugin. 

(2) Site key: Set the site key here that you have got from google reCAPTCHA.

(3) Secret key: Set the secret key here that you have got from google reCAPTCHA.