removing a stock cd player...! HELP

ok i have everything i need to install my stereo and i know how my only problem is, when i went to go install my aftermarket deck i can get the 24 pin clip out but there is a thick BLACK 18 or 16 gauge wire connected to the cd player, my car is a 2001 pontiac grand am se

my questions are

What is the black wire for?
and how do i remove it to install my aftermaket deck?

do i cut it or does it unplug...?

Thanx

the wire you refer to is the ground wire for your deck. cut it and then splice it to the wiring harness on your aftermarket deck.