The reCaptcha service is owned by Google, and it feeds a whole bunch of data, exactly what Google won't tell us, into one big machine learning algorithm that spits out a score how likely it thinks you are a bot, and depending on what that score is the site then deals with your request.. Checking the box is mostly unnecessary, and the newest versions of captcha don't even have it anymore, they just run silently in the background without you even knowing.