The Lenovo Flex has an HDD storage medium which is better than the SSD storage medium found on most laptops of a comparable spec and age to it. HDD is a traditional storage drive which stores the information on magnetic disks. HDD drives are slower than other forms of storage such as solid state drives (SSD) and flash drives.
This notebook PC's storage medium (HDD) is actually the worst storage medium amongst all similar spec portable PCs that came out around the same time as the Flex.
An SSD storage medium is the best storage medium amongst comparable types of notebook PC.