Ad 200 add on what is this?

I have the AD 200 pro. It his came with one of the AD200s. What is it for?!!! I know they connect to the flash and they are different colors. I’ve had my strobes for a while and literally just assumed it’s like a gel kinda? If so I get the different colors, but then it gets the question why the white?! Isn’t flash already white. And 2) how do I use it besides just plugging it in? tIA