Digital Certificate: Is to authenticate the identity of an individual or organization. They are granted by Certificate Authorities and typically contain the name of the person, organization, or Web site being certified along with a certificate serial number and an expiration date. Digital Certificates also include a public/private key pair. These keys and the digital certificate are used with secure Web pages to guarantee the Web pages are secure and actually belong to the stated organization. This is so users can know for sure who their credit card number or other sensitive data is really being sent to, in order to protect against some online scams.
Security protocols: In order to ensure the security of exchange of certificates between clients and servers, security protocols have been put in place such as SSL and TLS. The role of these protocols is to authenticate clients, authenticate servers, encrypt information being exchanged or ensure the integrity of information is being maintained. Since the encryption of information uses much space and slows the transfers, only the most sensitive transactions such as bank transactions are being encrypted.