Anyway, the basic story is that the Saturn had copy protection in the form of physical marks on the copy protected CDs. This puts a huge barrier to entry on homebrew and the like, so a guy going by Dr Abrasive tried to reverse engineer a way around that. He first looked into a way of disabling the copy protection on the CDs to allow burned CDs to be used but that proved too difficult.
He eventually hit upon the fact that the Saturn had an external module that could be added to allow the system to play video CDs. He then built a component to take advantage of that fact and feed in his own commands through this interface thereby avoiding the copy protection entirely. This allowed content to be run from USB sticks without the need for CDs at all, lowering the barrier to entry even more. It also helps workaround mechanical failure of the CD drive which is becoming a common problem for the 20 year old hardware.
So now if you have this custom built component, you can take an off the shelf system and start running code from a USB stick without any soldering, hacking, or modification at all beyond plugging the device into the back of the console.