reCAPTCHA is a security measure created by Google to help protect websites from spam, automated hacking tools, and cyber-attacks. These security measures are tests to distinguish between bots and humans. The tests are setup in a way that is easy for humans to solve, but very difficult for bots or other automated and malicious software to figure out.
This security tool blocks out malicious activity while allowing authorized users in; you will often see it when attempting to access a website. The test involves the user selecting photo boxes that have the item mentioned in the text field such as; traffic lights, cars, or bridges. Google has recently updated their reCAPTCHA to help with various parts of your security, watch the video at the end of this article to learn more.
Source: Google Support
Additional Reading: Cloudflare Dumps reCAPTCHA As Google Intends To Charge For Its Use
Related Terms: Bots, Botnets, & Bot Masters