Description
The Raspberry Pi Zero is half the size of a Model A+, with twice the utility. A tiny Raspberry Pi that’s affordable enough for any project!
 
Specifications:
1GHz single-core CPU
512MB RAM
Mini HDMI port
Micro USB OTG port
Micro USB power
HAT-compatible 40-pin header
Composite video and reset headers
CSI camera connector (v1.3 only)
 
Inputs and outputs:
MicroSD Card Slot: The Pi Zero gets its microSD card storage space, which you need to install the operating system on.
Mini HDMI: Video output for the Pi Zero is by way of a mini-HDMI connector. In terms of their operation, these authors perform the same as their larger versions. NB Mini-HDMI Fix HDMI adapter included with the Pi zero from element14.
Micro USB: You'll note there are two micro USB connectors on Pi Zero. One is for data (the connector is on the left if the MicroSD card slot is on the left), one is for power. Do not get them involved. Micro USB "on the go" to USB adapter is included with the Pi zero from element14 so you can connect USB hub, and therefore all your peripherals (keyboard, mouse, etc.).
GPIO: The Pi Zero has the same 40 pins for general-purpose I / O connections model A +, B +, and RPi2, but the pins are populated. So if you want to use GPIO, you either need soldering required pins in place or solder your connections directly to Pi Zero.
Run Pin Mode: There is two populated run pin mode, which can be used to connect a reset button to the Pi Zero. Again, you also need to add the pins yourself or solder a straight button to the board.
Composite Video: Here's an interesting one. The RCA has composited video output using two (populated) pins, so you can connect the Pi Zero up to older display equipment that receives the phono plug as input.
 
Resources:
1. Introducing Raspberry Pi Zero
2. Raspberry Pi Hardware