CA

The CA (Certificate Authority) is the entity that supplies digital certificates to other parties. The CA that supplies the certificate, specifies that the public key in the certificate belongs to the person, organization or entity that is mentioned in the certificate. The idea is that the CA will only supply certificates to entities it trusts. When a user sees a certificate from an entity that was signed by the CA that it trusts, the user can trust that the public key really belongs to the entity that is mentioned in the certificate.