Free SSL/TLS certificates are digital certificates that provide secure, encrypted connections between a web server and a browser. They help protect sensitive information, such as passwords and credit card numbers, by ensuring that data transmitted over the internet remains private and secure. Organizations like Let's Encrypt offer these certificates at no cost, making it easier for website owners to implement security measures. By using free SSL/TLS certificates, websites can gain user trust and improve their search engine rankings, as search engines often prioritize secure sites in their results.