If you're new to rugged computing and are hungry for a comprehensive-yet-understandable overview of what "rugged" means, I'd recommend that you read this article by Group Mobile Rugged Computers. They cover everything from non-rugged laptops all the way through rugged standards and IP ratings, wrapping up with the concept of price vs cost.

One note: you'll see that the definition of "fully rugged" can vary, e.g., they consider IP54 (standing up to a heavy spray) to be a "fully rugged" laptop. For those who need something more durable, our handhelds have an IP67 rating, which we differentiate with the term "outdoor rugged" -- standing up to dust and temporary immersion. If your application calls for working outdoors, be sure you know the IP rating of the computer you select. Weather is unforgiving, and you don't want to lose your device and your data to the elements.