An SSD and hard disk in the same drive. In a solid state hybrid drive, the OS may be stored in the faster SSD, or it may automatically migrate frequently used programs and data from the disk to the SSD.
A Temporary Solution
Hybrid drives have been essentially an interim solution, because SSD storage was more costly than the very mature hard drive technology. However, in the 2020s, SSD prices have dropped considerably and have become par with hard drives in many cases. See
SSD,
hybrid drive,
Fusion Drive,
SSD,
magnetic disk and
flash memory.