Based on your description I am going to assume that one of the water connections is only for filling up the Fresh Water holding tank on your RV. The other connection is the city water connection for using the water from the RV Park to run your faucets etc. This is the way a lot of older Motorhomes were set up. I cannot tell you which connection is which.
The best way to find out which is which to hook up an RV Drinking Water Hose to one of the connections and with the water pump off see if you have water going to your taps. If you do then you will know that is the one you should hook up to when you are at an RV park. When you are not hooked up to water you would use the water pump to pull the water out of your fresh water tank.
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