Lastly, the Optane SSD. The minimum latency at 4KB is only 12μs, which is an astonishing result that is about 10 times faster than NVMe SSD and 1000 times faster than HDD.

The first is a SATA SSD, which comes in a 2.5-inch form factor and connects to your motherboard with the same cables and ports as a SATA HDD. The second (and newer) is the M.2 SSD.