[1] There are three main types of Digital Certificates, they are:
All Digital Certificates come from a Certificate Authority [7] which is a computer system that is capable of issuing the different types of Digital Certificate. The online flash presentation of Digi-CA™ [8] explains the benefits in a simple and easy to understand manner.
Links:
[1] https://www.digi-sign.com/downloads/download.php?id=digi-ca-pdf
[2] https://www.digi-sign.com/ssl+certificate
[3] https://www.digi-sign.com/digi-code
[4] http://www.digi-sign.com
[5] https://www.digi-sign.com/aacd
[6] https://www.digi-sign.com/two+factor+authentication
[7] https://www.digi-sign.com/certificate+authority
[8] https://www.digi-sign.com/demos/aacd