Internet keys are USB modems that provide internet to laptops. Unlike hotspots or using your phone, they rely on the laptop battery.
If you have tablets or want to share the connection with more than one device at the same time. A mobile hotspot is preferred.
Note if you have a smartphone, there's a mobile hotspot feature on the newer phones. I often use my BlackBerry 9810 or Q10 to give my wifi iPad internet connection when travelling. Warning, the hot spot feature drains batteries double or triple times faster.
With regards to camping...