The Stream 13-c025na has an SSD storage medium which is better than the HDD storage medium found on most medium processor core laptops that are a comparable age to it. 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 actually the best storage medium amongst all medium processor core laptops that have been available for around the same time as the Stream 13-c025na.
An HDD storage medium is the worst storage medium across similar types of notebook PC.