A certificate authority issues and signs certificates that other systems may trust as part of a public key infrastructure.
A certificate authority, usually called a CA, is an entity that issues and signs digital certificates. In plain language, it acts as a trusted issuer that says a given public key belongs to a stated identity under a defined trust process.
A CA matters because trust on public networks and in enterprise systems often depends on whether a certificate came from an issuer the relying system recognizes. If the issuing authority is not trusted, the certificate may be rejected even if its cryptography is technically valid.
It also matters because the CA sits close to the center of the trust model. Weak issuance practices, poor protection of CA systems, or mistaken certificate issuance can affect many downstream services and users.
Certificate authorities appear in public web trust, internal PKI, code-signing programs, enterprise device identity, and service certificate issuance. Browsers and operating systems maintain trusted roots, while organizations may also run internal CAs for private systems and workloads.
Security teams review CA choices, issuance policies, trust-store configuration, renewal processes, and revocation handling. A compromised CA or broken internal trust configuration can create both security and availability problems.
An organization runs internal services that are not exposed publicly. Rather than buying public certificates for every internal hostname, it operates an internal CA that issues certificates trusted by managed corporate devices. Those devices accept the internal CA because it is in their trusted root store.
A certificate authority is not the same as the entire Public Key Infrastructure. The CA is one issuing component within a broader trust and lifecycle system.
It is also not the same as a Digital Certificate. The CA issues certificates, but the certificate is the artifact presented to relying systems.