Raspberry Pi GPIO Pinout: What Each Pin Does on Pi 4, Earlier Models
The Raspberry Pi has 40 GPIO pins that connect to sensors, lights, motors and other devices. Heres a map and detailed explanation of what each does, including on the Pi 4.
Raspberry Pi Foundation Philips Semiconductors General Purpose Input Output Hardware Attached Purpose Input Output Light Emitting Diodes
Source: tomshardware.com