There are usually 2 jacks. One is for Over-the-air television reception through your camper antenna. Outside, there is also a jack where you can plug in an external cable television service (like at a campground). This same jack can be used (outside) to run a television from your camper's antenna.
A second jack should be available for hooking up a satellite television system. DishTV and DirectTV will not work going through your trailer television booster. If you have a satellite system, the coax cable connects to the external satellite antenna to the outside jack on the camper marked, "satellite". That is wired directly to another jack inside the camper. From that jack, another coax is needed to connect the satellite receiver. And from the satellite receiver box, usually an HMDI cord to the actual television.
The little button is the booster for the camper's antenna. More than likely, it should be "on" all the time. When it's "on" there should be a little green light that come on too.
If you run an external DVD player, that might be WIFI ready, that will be run separate, and has nothing to do with the wiring in the camper. Usually, they are connected from the DVD player to the television with an HMDI cord as well.
We have found that in campgrounds where they offer cable hook up, the booster button (green light) has to be turned off. Otherwise, the cable does not work.