In the remote control you have a button in which you can choose between different collars. It's saved in the memory the stim to each one, by example Dog1 uses stim in the 2 level and Dog2 uses stim in the 3 level, when you switch between 1 and 2 collar, every dogs get their own level stim.
Basically, two or more collars and only one remote control.
I have one of those because I bought it used and it was the one available, but never used it in two dogs, nor I think I'd be comfortable with. Too many chances of making a mistake and stimulating the wrong dog, at least for fine training. But I can see how it can be practical for hunters or if you have more than one dog, want to do a trip with the dogs off-leash and want the collars only as a extra safety tool.