Okay kiddo, so you know how there are different types of computers that people use? Some are big and some are small, and they might run on different types of processors. Well, when people try to make software that can work on lots of different types of computers, they have to be really careful to make sure that it will work on all of them.
Shellcode is a type of code that bad guys can use to try to take control of a computer. But if they want to use the same shellcode on lots of different computers, they might have a problem. Different computers might have different processors, which means that they work in different ways.
That's where multi-architecture shellcode comes in. It's like a special kind of shellcode that is written to work on lots of different types of computers. It's like a magic trick - it can figure out what type of computer it's on and change itself to work with it. That way, the bad guys only have to write one version of the shellcode, and it will work on lots of different computers.
But don't worry, most people who write shellcode are good guys who are trying to help keep computer systems safe. They want to make sure that their code works on lots of different computers too, so they use multi-architecture shellcode to make sure that it will work for everyone.