Public Key Infrastructure
The system which provides a way to securely share public keys of websites/orgs over the internet.
This system generates and verifies public key certificates with a standard format like x_509
Certificate Requests
Organisations (subjects) can generate a certificate request, which will be sent to a Certificate Authority for verification.
Certificate Authority
An organisation who has rights to certify the certificate requests.
Names of some of the CAs: IdenTrust , DigiCert Group, Let’s Encrypt