The easiest way to explain it would be. Every device phones etc have a recovery mode just incase you screw up the internal software or an update bricks your device for some reason . You or some worker at the company can then press a certain key combination like hold the power button and press left 2 times(something to that effect) then you can put in some code to fix your device. Well game consoles patch out recovery modules so that people don't use it to put in unauthorized code that can crack there console, Anyway Nintendo uses The NVidia Tegra chip That was used for other devices before being put into the switch. Since it was used for other devices it was bound to have a security flaw since it wasn't exclusively used by Nintendo products. Nintendo asked them to take out the recovery mode but NVidia did a suuuuper shitty job patching it out on a hardware level. You need an button extra button that the switch doesn't have to get into recovery mode. The function is hold Volume Up+Power+ ? button. Luckily you can emulate the ? button by shorting to pins in the right controller rail of the switch. Then bam you are in recovery mode and can put unauthorized code into the switch via recovery mode. It what crackers would call a back door. Now you have an exploit which is honestly the "easy" part. Then a bunch of awesome coders have a starting point to use custom written code to get access to the nand and kernel which is pretty much holds the systems security and permissions access and the Operating system. I am not entirely sure how the teamexecuter mode chip works though. My guess would be after Nintendo completely patched out the recovery mode(properly this time) Team Ex just wrote the recovery to a chip and piggy backed it onto the tega chip and switched around the boot access by soldering the nand chip to different parts of the board. Emulating the original recovery access of the v1 switches. Which I imagine was about difficult as hell. I hope this helped I tried to dumb it down the best I could.