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In 2015, Intel and Micron unveiled 3D XPoint memory, a new competitor to flash memory that promised significantly higher performance and endurance. Several years later, Intel has successfully commercialized 3D XPoint memory in a growing range of Optane products, but other alternative non-volatile memory technologies are still largely stuck in the lab.
To compete against Intel's Optane SSDs, Samsung decided to exercise their lead in 3D NAND flash memory to produce a specialized high-performance variant, which they call Z-NAND. Fittingly, the first SSDs they use it in are branded "Z-SSDs". The first two models to be released were the SZ983 and SZ985, which were both high-end drives specifically for datacenter customers.

Meanwhile, with their major datacenter customers taken care of, Samsung is moving to make more of their enterprise and datacenter storage products available through retail distribution channels instead of just large-volume B2B sales. Spearheading that initiative, the SZ983 is now being sold to retail customers as the Samsung 983 ZET.

Enter the 983 ZET: Going Back To SLC

Samsung originally announced Z-NAND in 2016, a year after 3D XPoint memory was announced and before any Optane products had shipped. Fundamentally, the first generation of Z-NAND is an effort to turn back the clock a bit; to step back from today's modern, high-density, (relatively) high-latency Triple Level Cell (TLC) NAND and back to simpler Single Level Cell (SLC) designs.

Full reading: https://www.anandtech.com/show/13951/the-samsung-983-zet-znand-ssd-review