Raspberry Pi is the microcontroller or mini computer.
The GPIO - General Input and Output pins and i have listed below the use caused of the pins
Pin Definitions
PWM - Pulse with modulation - based on frequency modulation these pins are working => GPIO12, GPIO13, GPIO18, GPIO19
SPI - Serial Peripheral Interface - to communicate and data transfering with other devices forms synchronly (bit by bit) => SPI0: GPIO10,GPIO9,GPIO11,GPIO8,
GPIO20 , GPIO19 , GPIO21 , GPIO18 , GPIO17 , GPIO16
I2C - Inter integrated circuit - its used to connect other microcontrollers or devices => GPIO2 , GPIO3 ,GPIO0 , GPIO1
Serial Pins- GPIO14 , GPIO15
Other Volatage pins are I/O pins - based on your purpose you can use it.
if your more definition here