The pins on the Raspberry Pi are a little complicated. There are multiple headers on some Raspberry Pis with extra pins, and the pin numbers are not consistent between Raspberry Pi board versions.

To help make it easier, you can specify pins in any of the following three ways:

1. By function, e.g. 'GPIO18'
2. By physical Pi pin number, e.g. 'P1-7'. The format is 'P[header]-[pin]'
3. By WiringPi virtual pin number, e.g. 7

Note: If you specify a Number instead of a string, it is assumed to be a WiringPi number.

Note: Each pin is given a peripheral name, and is one of a few possibilities:

Here is a table of the pin mappings on all of the support Raspberry Pi boards.