Hi, welcome to the forums.
The message pretty much means what it says, for whatever reason, your connection to your ISP (3 wireless) has been terminated. This happens from time to time. I use the Verizon USB broadband card when I am on the road and periodically get drops like this.
If it is happening often, to the point of your service becoming non-usuable, you may want to call your ISP, otherwise, simply reconnect.