The MacBook Air Mid 2012 has an HDD storage medium which is better than most MacBooks that have been on the market for a similar time to it. Most MacBooks that have been around for a comparable time to it have an SSD storage medium. 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 across all MacBooks that were launched more than two years ago.
An SSD storage medium is the best storage medium amongst comparable types of notebook PC.