It could be to run an an onboard fridge while driving.
It could be to charge an onboard battery while driving.
It may be able to do both.

But without more info as to what electrical gear your camper trailer contains with some detail as to what wires connect to those items, it is hard to be sure.

If you can do a bit of investigation the answer may become evident.
If not, put up what you have found and you may get an answer.
Details of the make/model/year of the unit would help too.

Follow it back to see what it is connected to.......

G'day Cardiel Bob,
If your camper has a 3-way fridge it's safer to run it through the higher current rated (generally 50A) Anderson plugs rather than the so called "heavier duty" pins on a 12 pin plug, socket. You can chance melting the latter.
If you are running a 3way fridge & you make a few stops during the day to reduce the chance of flattening your car's battery, a Fridge Switch (operates on motion) should be fitted.

The plugs come in various sizes but the grey 50A ones are the most widely used.

If you haven't had a look, there is a stack of information stored away in this forum - just do a "Search" or "Advanced Search" - if you can't find it, by all means post a question in the most suitable page but give as much information as possible, perhaps a photo, model number, etc.

There is another forum that I found useful when we had camper trailers - campertrailer.org.au (they have gone to Facebook these days) but there's a lot of good stuff still on the original website.

To answer the question... The Anderson plug is a very, heavy duty 12 volt supply to your Van or Camper. To run your 12 volt items while you travel, to charge your 12v battery while you travel, can be used in conjunction with Solar panels to charge the battery, plus run some 12 v items. Can be used with a portable Generator.. What have I missed..