The main function of an SSL certificate is to establish a secure, encrypted connection between a web server and a browser. This technology is crucial for protecting sensitive information, such as login credentials and payment details, from potential interception by third parties. When a website uses an SSL certificate, it enables HTTPS (Hypertext Transfer Protocol Secure), which creates a secure channel for communication. SSL certificates also authenticate the website's identity, assuring users that they are interacting with a legitimate site, ultimately fostering trust and security in online transactions.