NYT explores the difference between a solid state hard drive and flash memory that you normally find in USB thumb drives or memory sticks. Apple MacBook Air laptop is available either with regular hard-disk or the solid state hard drive. Excerpts:

"Unlike a traditional disk-based hard drive, which is made of spinning magnetic disks, motors and other hardware, a solid-state hard drive has no moving parts to break down or wear out.

It can better withstand bumps, bangs and other physical realities of portable computing. The downside is that solid-state hard drives are much more expensive than hard-disk drives." Link.