This chapter introduces internet of things (IoT), internet of things vision, basic architecture of the internet of things, IoT security, and lightweight cryptography. It provides a basic understanding about internet of things and its nuts and bolts. Kevin Ashton, A founder of Auto-ID Center at MIT sparked a word "Internet of Things (IoT)" in 1999 during a proctor and Gamble presentation. The base level in IoT consists of identity enabled smart machines. These smart machines can be sensors, actuators, devices capable to sense, read, hear, think, see and communicate. IoT provides tremendous opportunity to the device manufacturers, application developers and internet service providers. The chapter discusses application, thing, communication and research-oriented vision. It discusses sensor, fog, communication, data, cloud, mobile and security as service concept. The chapter talks about various attacks that can be caused in Retail industries use radio frequency identification (RFID), edge computing and communication.