Ramps 1.4 Pins to pins.h in Marlin Q (1 reply)

Could anyone explain to me the relationship between the placement of the pins on the ramps 1.4 board to the pins.h configurations. I am having a hard time understanding how to locate individual pins.

For example My Motherboard = 33. why is "#define FAN_PIN 9" what does the 9 stand for? is there a map that can be superimposed onto the ramps 1.4 blueprint to match Marlin assignments?

Apologies for Newb Questions(:D

Janski

#if MOTHERBOARD == 33 || MOTHERBOARD == 35 || MOTHERBOARD == 67
    #define FAN_PIN            9 // (Sprinter config)
  #else
    #define FAN_PIN            4 // IO pin. Buffer needed
  #endif

  #if MOTHERBOARD == 77
    #define FAN_PIN            8 
  #endif
  
  #if MOTHERBOARD == 35
    #define CONTROLLERFAN_PIN  10 //Pin used for the fan to cool controller
  #endif

  #define PS_ON_PIN          12

  #if defined(REPRAP_DISCOUNT_SMART_CONTROLLER) || defined(G3D_PANEL)
    #define KILL_PIN           41
  #else
    #define KILL_PIN           -1
  #endif

  #if MOTHERBOARD == 35
    #define HEATER_0_PIN       8
  #else
    #define HEATER_0_PIN       10   // EXTRUDER 1
  #endif

  #if MOTHERBOARD == 33 || MOTHERBOARD == 67
    #define HEATER_1_PIN       -1
  #else
    #define HEATER_1_PIN       9    // EXTRUDER 2 (FAN On Sprinter)
  #endif

  #define HEATER_2_PIN       -1