The X.509 Version 3 certificate goes beyond the X.500 standard with its provisions for unique identifiers. Certificate serial number. Signature algorithm identifier. Subject X.500 name. Certificate Authority's digital signature.
Certificates attest to a linkage or an association, an origin or ownership.
For example, a passport links a person to citizenship. A driver's license links a person to the right to drive in a given state. A car registration links an automobile, an owner and the payment of appropriate fees to a state. An employee card links person and employer, and confers authority. A membership card relates a person to a club and associates that person with a member s rights.