digital certificates - Definition from the Hotspot Shield Glossary
Digital Certificates are used in the transferal of data over the internet in a secure manner and to show that a person, device or organization is legitimate.
A digital certificate works in much the same way that a traditional passport does - It is issued by a trusted authority, contains information that can be used to identify the holder, and cannot be forged or duplicated. A certificate will contain the following: a unique serial number, expiration dates, a digital signature of the issuing body, the certificate holders name, and their public key.
The digital signature is required to show that the certificate has been is distributed by an official body, and the public key is used for encryption. Web browsers and Operating systems will keep an updated list of root certificates that are trusted and verified.