(Red dots are different variables)
If you interact with variable then it changes !but nothing else!
If you interact with group then it interacts with everything inside in same way (for example you could give command to trigger on event to change this group to 100, and everything inside of group changes to 100, or multiply by..., divide by...)
But of-course I'm just a random person who doesn't know about code anything at all so I probably am mistaken. Thanks for reading!