The purpose of a root certificate in internet security is to establish a trust hierarchy between users and trusted Certificate Authorities (CAs). Root certificates are self-signed and serve as the foundation for a chain of trust in digital communication. When a user connects to a secure website, their browser checks if its root certificates validate that website's security certificate. If the certificate is verified, secure SSL/TLS connections can be established, ensuring the authenticity of the website and protecting against man-in-the-middle attacks. This critical element enhances users' confidence in online transactions.