Everyone likes a smooth, sanded surface on a project, but no one (and I mean absolutely no one) like the tedious process of getting it done. Motorized sanding machines speed up the process greatly, but many of them can be hard to control, or wind up leave swirl marks in the finished surface.
Not so with the random-orbit sander. As the name suggests, its pad follows an entirely random pattern, so you can control the amount of wood removed, and leave your surface free of spirals.
They're great for all kinds of DIY projects, and the only handheld sander I'd recommend for your toolbox.