The HP SlateBook 14-p000na has an SSD storage medium which is better than the HDD storage medium found on most similar spec notebook PCs that have been available for around the same time as it. 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 that are a similar age to the SlateBook 14-p000na.
An HDD storage medium is the worst storage medium amongst comparable types of notebook PC.