The Lenovo P300 SFF has an SSD storage medium which is faster than the HDD storage medium found on most PCs of a similar age and type to it. Solid State Drives (SSD) store information in transistors on a circuit board rather than on optical or magnetic media. This has the advantage of being much faster than a traditional HDD drive.
An SSD storage medium is actually the best storage speed amongst all computers of a comparable age and spec to the P300 SFF.
An HDD storage medium is the worst storage speed amongst comparable types of personal computer.