SSL (Secure Sockets Layer) is a security protocol designed to ensure security and data integrity for Internet communications. Based on the SSL protocol, an SSL certificate can be installed on the server to achieve encrypted data transmission.
Certificate Authority (CA) is a third-party authority that verifies the validity of public keys. It is responsible for specifying policies and procedures to verify users' identities, sign SSL certificates, and ensure the identity of a certificate holder and ownership of a public key. The CA issues an SSL certificate for each user using the public key. A SSL certificate is used to certify that individuals/businesses listed in the certificate lawfully own the public key listed in the certificate. Digital signatures from CA can prevent certificates from being forged and tampered.
An SSL certificate actually represents the verification of the public key from CA, which contains digital signing authority information, user information of the public key, the public key, authority signature, and expiration date.