What can I use Digital Signature Certificates for:-
                                      Three uses are outlined here. Your Digital Signature Certificate could be used to allow you to access membership-based web sites automatically without entering a user name and password. It can allow others to verify your "signed" e-mail or other electronic documents, assuring your intended reader(s) that you are the genuine author of the documents, and that the content has not been corrupted or tampered with in any way. Finally, Digital Signature Certificates enables others to send private messages to you: anyone else who gets his/her hands on a message meant for you will not be able to read it.

How important is the use of Digital Signature Certificates to me:-
                                   Digital Signature Certificates and the CA are just two elements of the Public Key Infrastructure (PKI), an overall Internet security system. Once the PKI is operational, everyone who has a Digital Signature Certificate can be traced and held accountable for their actions. Consequently, uses for the Internet, which could not be fully realized before, will finally take off: electronic banking and commerce (funds transfer, buying and paying on-line), on-line transactions with government agencies (applying for and renewing ICs, licenses, paying fines and bills), and on-line transactions between businesses. The day when the only way to do some of these transactions is through the Internet may not be too far off. Everyone who wants to be part of it will need Digital Signature Certificates.

What different kinds of Digital Signature Certificates are there:-
                                Digital Signature Certificates can be categorized into Server certificates and Personal certificates. The differences lie in the information they contain and who they identify. 

What are personal certificates:-
                               Personal certificates serve to identify a person. It follows that the contents of this type of certificate include the full name and personal particulars of an individual. Among other uses of personal certificates some are: Secure e-mail correspondence, and Enhanced access control to sensitive or valuable information.

What do you mean by the Public Key Infrastructure (PKI):-
                             The PKI is the overall system of identifying parties on the Internet using their certificates. It is headed by a Certifying Authority that is responsible for issuing and verifying the validity of the Digital Signature Certificates.