We have an Acer Netbook what is difference between hotspots & hotel wi-fi access?

We nave an Acer Netbook & paying for monthly data usage (500Gb) I believe.  My husband is in a hotel with build-in wi-fi he can hook up to.  Is our data usage getting used even though he is using their wi-fi system?  If so, I need to reduce his monthly data fees if they aren't going to come into play as long as he's using the hotel's wi-fi.   Or do Wi-Fi hotspots only allow these wi-fi situations where data isn't used?