Before we setup the Pi and get software installed, it’s a good idea to take a look and familiarize yourself with the location and orientation of the GPIO pins and components. Take a look at the images here:

Please note the orientation of the boards, the GPIO pins should be on the right of the board. The Top left pin is Pin 1. With this orientation in place, you can now reference the below image:

The numbers in the center represent the physical GPIO pins on the Raspberry Pi. The next set on either side represents BCM, these are the numbers associated with the breakout module, and other devices that use the BCM numbering system. Lastly is WiringPi, which assigns different numbers to these pins. Depending on the device, you will be asked for a BCM, WiringPi, or a GPIO pin so it is important to familiarize yourself with each of these numbering systems.

If you have a device plugged into BCM 17, it also functions as WiringPi pin 0, and GPIO pin 11.