ROM files vs cartridge: what's the real difference?

the rom may be a perfect copy of the cartridge data, but you have to have something to put the rom file on so that the system can play it. Due to the complexity of the system and it's security, as opposed to previous generations of nintendo handhelds, the exploits are needed to get the flash card to work properly. an exploit/mod would be needed to get the system to load a rom from the 3ds's SD card as well.

Edit:
Basically, the cartridge is a physical thing which contains data, the rom is just the data itself.

 

But what's stopping someone from putting a single rom onto a GW and having it emulate a cart. How can a 3DS tell if it's an official cart or not?

 

I'm pretty sure it has to do with the way the gateway card works. I'm sure there's nothing stopping anyone from creating a 1:1 cartridge clone, but it'd be kinda pointless unless you wanted to hook it up to your computer to swap out roms because there'd be no chance of multi-rom, and no chance for homebrew either.

 

Correct me if I'm wrong, but isn't that basically what Gateway did before they had multi-rom support? You had to actually write a single rom directly to a microSD card and Gateway would emulate a cartridge of that game.

 

The signature is still intact, or early Gateway versions wouldn't run them as the signature checks were still in place. But cartridge communication is encrypted along with other things that make it hard to create a flashcart that works exactly like a real cartridge.

 

The topic is the difference between a rom and the game data inside a cartridge. If it is not copied 1 to 1 from a cartridge does that mean the game on rom is not the same game as on a cartridge ?