The ATIV Book 9 has an SSD storage medium which is better than most portable PCs of this age and type. Most notebook PCs of a similar spec and age to it have an HDD storage medium. Solid State Drives (SSD) store data in semiconductors on a circuit board rather than using magnetic or optical media. Solid State Drives have no moving parts which makes them very fast and reliable.
An SSD storage medium is in fact the best storage medium across all notebook PCs of a comparable spec and age to the ATIV Book 9.
The worst storage medium amongst similar types of notebook PC is HDD.