A Certification Authority (CA) is a trusted entity that issues digital certificates to verify the identity of individuals, organizations, or devices. These certificates are essential for establishing secure communications over the internet, as they help ensure that the parties involved are who they claim to be. CAs play a crucial role in the public key infrastructure (PKI), which underpins many security protocols, including SSL/TLS. When a user connects to a website, their browser checks the site's digital certificate against a list of trusted CAs. If the certificate is valid and issued by a recognized CA, the connection is considered secure. This process helps protect sensitive information, such as passwords and credit card numbers, from being intercepted by malicious actors.