Public key infrastructure (PKI) is the framework used to issue, maintain, and revoke public-key certificates — the system that lets parties verify identities and exchange data securely using digital certificates.
What it means
Per NIST, PKI is the framework that creates, manages, and revokes public-key certificates. Those certificates bind an identity to a cryptographic key, which is what makes secure websites (HTTPS), signed code, and encrypted email trustworthy. PKI concepts appear in security, identity, and infrastructure roles.