Digital certificates are electronic documents that verify the authenticity and integrity of entities, such as websites or individuals, in a networked environment. They are issued by trusted Certificate Authorities (CAs) and contain information such as the entity's public key and identification details. Digital certificates are used for various purposes, including secure communication (e.g., SSL/TLS certificates), email encryption (e.g., S/MIME certificates), and code signing. CAs play a crucial role in network security by validating the identity of entities and ensuring the trustworthiness of digital certificates.