The Asus EeeBook X205TA has an SSD storage medium which is better than most notebook PCs of a similar age and type to it. Most notebook PCs that have been around for a similar time to it have an HDD storage medium. Flash drives store data in semiconductors on a circuit board rather than using magnetic or optical media. Flash have no moving parts which makes them very fast and reliable.
An SSD storage medium is in fact the best storage medium amongst all notebook PCs of a similar spec and age to the EeeBook X205TA.
An HDD storage medium is the worst storage medium across comparable types of laptop.