Hardware What is the GPIO sleep switch?

[ARandomOSDever]

So I was reading the 3DBrew page for the bootrom and I came across this:

ff: sleep switch state (2==MCU sleep switch closed, 1==GPIO sleep switch closed (very bad if this happens), 0==sleep switch open)

I assume the MCU switch is the one triggered by the speaker when closing the system but what is the GPIO switch and why is it "very bad" to be closed?