The Raspberry Pi Zero is a small computer that costs about $5 and smaller than a credit card, designed by the Raspberry Pi Foundation (a nonprofit organization with the mission to teach computer science to students, especially those who lack of access to the requisite tools). The Raspberry Pi Zero was preceded by the Raspberry Pi Models A and  B. A detailed history of the Raspberry Pi and the different models of the Raspberry Pi is available on http://elinux.org/RPi_General_History. The Raspberry Pi Zero was released on 26th November 2015 (Thanksgiving Day).

The Raspberry Pi Zero is powered by a 1 GHz BCM2835 processor and 512 MB RAM. BCM2835 is a System on a Chip (SoC) developed by Broadcom semiconductors. SoC is one where all the components required to run a computer are available on a single chip (for example, the BCM2835 includes CPU, GPU, peripherals such as USB interface). The documentation for the BCM2835 SoC is available at https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/README.md.

Let's briefly discuss the features of the Raspberry Pi Zero using the preceding picture marked with numbered rectangles:

1. The mini HDMI interface: The mini HDMI interface is used to connect a display to the Raspberry Pi Zero. The HDMI interface can be used to drive a display of maximum resolution of 1920x1080 pixels.
2. USB On-The-Go interface: In the interest of keeping things low cost, the Raspberry Pi Zero comes with a USB On-The-Group (OTG) interface. This interface enables interfacing USB devices such as a mouse and keyboard. Using a USB OTG to USB-A female converter. We need a USB hub to interface any USB accessory.
3. Power supply: The micro-B USB adapter is used to power the Raspberry Pi zero, and it draws about a maximum of 200 mA of current.
4. micro SD card slot: The Raspberry Pi's operating system (OS) resides in a micro SD card and the bootloader on the processor loads it upon powering up.
5. GPIO interface: The Raspberry Pi Zero comes with a 40-pin general purpose input/output (GPIO) header that is arranged in two rows of 20 pins. The Raspberry Pi Zero's GPIO interface is shipped without a soldered header. The GPIO header is used to interface sensors, control actuators, and interface appliances. The GPIO header also consists of communication interfaces such as UART and I2C. We will discuss the GPIO in detail in the second chapter.
6. RUN and TV pins: There are two pins labeled as RUN below the GPIO header. These pins are used to reset the Raspberry Pi using a small tactile switch/push button. The TV pin is used to provide a composite video output.
7. Camera interface: Raspberry Pi Zero boards (version 1.3 or higher) come with a camera interface. This enables interfacing a camera designed by the Raspberry Pi Foundation (https://www.raspberrypi.org/products/camera-module-v2/).

All these features of the Raspberry Pi have enabled them to be used by hobbyists in projects involving home automation, holiday decorations, and more, limited only by your imagination. Scientists have used them in experiments, including tracking of bees, tracking wildlife, perform computation-intensive experiments. Engineers have used the Raspberry Pi to build robots, mine bitcoins, check Internet speeds to send Twitter messages when the speeds are slow, and order pizza!