What is the story behind this DC-DC charger?
Why would you need one?
It will use input from either your Anderson plug on the back of your tug, or a solar panel, and boost (if required) the voltage to enable the best charging conditions for the battery in your camper.
There are other ways of skinning the cat, but these things look after your battery and will manage to get them charged to close to 100% capacity.
I have one in my camper, and also have a 40amp AC-DC power supply connected to the 'alternator' input, which allows me to charge when plugged into AC power as well.
Seems to work pretty good.