What is SD_CD Pin used for on SD card module

The SD card and SD Micro modules have a pin called SD_CD.
The G120 Pinout does not have a SD card pin lebeled like that.
The Cobra II Schematic shows that it is connected to P1.8 there, and it works well with my G120HDR if I do the same.
But what is this pin for?
CD might be Card Detect, but card detect should be handeld by SD_D3.
Can I change the pin (P1.8) somewhere in software?

CD = card detect. Use any pin.

public static bool DetectSDCard()
use the SD_CD pin?
If not, can I just leave it away.