About the NDEF Format
---Quote from Adafruit by lady ada
NDEF (NFC Data Exchange Format)
The NFC Data Exchange Format (NDEF) is a standardised data format that can be used to exchange information between any compatible NFC device and another NFC device or tag. The data format consists of NDEF Messages and NDEF Records. The standard is maintained by the NFC Forum and is freely available for consultation but requires accepting a license agreement to download.
The NDEF format is used to store and exchange information like URIs, plain text, etc., using a commonly understood format. NFC tags like Mifare Classic cards can be configured as NDEF tags, and data written to them by one NFC device (NDEF Records) can be understood and accessed by any other NDEF compatible device. NDEF messages can also be used to exchange data between two active NFC devices in "peer-to-peer" mode. By adhering to the NDEF data exchange format during communication, devices that would otherwise have no meaningful knowledge of each other or common language are able to share data in an organised, mutually understandable manner.
Some helpful app notes and white papers relating to NDEF are listed below:
NDEF Messages are the basic "transportation" mechanism for NDEF records, with each message containing one or more NDEF Records.
NDEF Records contain a specific payload... More info visit: https://learn.adafruit.com/adafruit-pn532-rfid-nfc/ndef