The function of a digital certificate is to authenticate the identity of individuals, organizations, or devices online. It serves as a form of cryptographic proof that validates the ownership of a public key, creating a secure communication channel. Digital certificates are commonly issued by Certificate Authorities (CAs) and are essential in establishing secure connections over the Internet, such as in SSL/TLS protocols for websites. They help ensure data integrity and confidentiality by enabling secure data exchange between parties, enhancing trust in online transactions and communications.