Filtering for NFC Intents:

To start your application when an NFC tag that you want to handle is scanned, your application can filter for one, two, or all three of the NFC intents in the Android manifest.

Usually you want to filter for the ACTION_NDEF_DISCOVERED intent for the most control of when your application starts.But ACTION_TECH_DISCOVERED intent is a fallback for 

Near Field Communication



Near Field Communication (NFC) is a set of short-range wireless technologies, typically requiring a distance of 4cm or less to initiate a connection. NFC allows you to share small payloads of data between an NFC tag and an Android-powered device, or between two Android-powered devices.




Tags can range in complexity. Simple tags offer just read and write semantics,