What makes a drive rugged is the casing around it, which allows these drives to withstand shock, dousing, and the like. It's also something of a misnomer, as the actual drive mechanism inside the tough shell is usually a normal, off-the-shelf storage component, just like you'd find in any laptop or desktop.
Drives designed for more casual abuse are often marketed as 'ruggedized,' but that's an inexact term. Some rugged drives are built to withstand forces that would kill any bare-naked internal drive: strong impacts, water immersion, even fire.
