Most passports worldwide are Machine Readable Passports (MRP), meaning there is printed information on the identity page (also known as the data page) that can be scanned with an optical reader.
The main advantage of MRPs was faster processing of arriving passengers by immigration officials. An electronic passport, or epassport, is the same as a traditional passport with the addition of a small integrated circuit (or "chip") embedded in one of the covers or pages. The chip adds digital security features, including biometrics, that show the passport is authentic and the information in the chip has not been altered. These features prevent counterfeiting and better link the passport to its owner.
For more information, see the biometric passport tutorial or click on the epassport tag above.