NFC, or Near Field Communication, is a technology that was recently added to the iPhone 6 and 6 Plus in order to implement Apple Pay. The NFC chip included on these devices is the PN548[dead link] by NXP Semiconductors. It is similar to the chip used in the Galaxy Nexus, and possibly other Android devices.
Apple's implementation of NFC is split into a number of binaries, found only on iPhone7,1 and iPhone7,2 devices:
Passbook uses NearField.framework to communicate with nfcd, and nfcd uses the NFC library provided NXP to communicate with the PN548 device. PN548.dylb is NXP's libnfc-nxp, which is open source as a part of Android. PN548_API.dylib is written on top of PN548.dylib, abstracting away the full functionality of libnfc into a CoreFoundation style API named NFDriver for the express purpose of card emulation.