Ruth, a "hot spot" is a location on the ship where your computer can connect wirelessly (using "Wi-Fi" or similar) to the internet. It used to be that one had to go to the ship's internet cafe to use a computer to get onto the internet. Now, many ships have installed equipment such that you may be able to sit in a lounge or other public room, or even in your cabin, and use your own Wi-Fi enabled computer to sign onto the internet. But, as I said, no matter where you are physically sitting with your computer, be it the internet cafe or elsewhere on the ship, the price of getting onto the internet is the same.
By the way, "hot spots" have the same definition on dry land, too. For example, all of our local Barnes & Noble store is a hot spot, meaning you can take your own laptop to that bookstore and sit in the cafe or on any chair in the store, and sign onto the internet. Some places, like the Ft. Lauderdale airport, don't even charge for this service.