Near Field Communication (NFC) is an radio frequency (RF) based proximity coupling technology allowing transactions within a range up to 10 cm. With NFC, a key technology is on its way into the consumer´s most personal device, allowing the customer to use his devices for secure services such as payment or ticketing but also for service initiation or data exchange. Interoperability is one of the most important goals to be achieved prior to roll out devices and services, in order to satisfy the consumer´s expectations. This chapter deals with different operating modes and use cases that can be im- plemented with NFC technology with ghe main focus on mobile phones. This high level description is backed up with a look into the hardware architecture for NFC as well as the software stack in mobile phones. The chapter ends with a description of tags and tag-formats for the NFC ecosystem.