Good day everyone!

I recently purchased a Mazda Drifter 2.5 Diesel and I would just like to know if someone could explain to me what the RFW does? I have read up about it on the internet a bit, but I am still a bit confused. To my understanding, whilst you are driving in 2H and you want to change to 4H then you can first put on RWP and then you may change the lever from 2H to 4H whilst driving. Am I correct saying this or do I have a wrong understanding here?

And what do they mean when they refer to hubs?

Sorry, my knowledge is a bit weak about this.

Thanks in advance!