NVMe stands for Non-Volatile Memory Express. Let's first see what "Non-Volatile Memory" is. It's simple, it's the memory that retains its data when the power supply is cut off, the opposite of RAM, and it has been around us forever. From Floppy Disks to SSDs. 

SATA SSDs and SATA M.2 SSDs use the SATA communication protocol, while NVMe M.2 SSDs take advantage of PCI Express. That's where the "Express" in the name comes from and also their main difference.

SATA SSDs and SATA M.2 can reach up to 600 MB/s, while NVMe M.2 rely on the current PCI Express version, with the fastest at the moment being the Crucial T700 with a speed of 12,400 MB/s, which is 20.6 times faster than the theoretically fastest SATA SSD. The 5th Generation PCIe NVMe are relatively new, and I can't wait to see their ceiling.

Nowadays, NVMe SSDs are becoming more and more accessible to consumers day by day, with the price now being almost the same as a "top" SATA SSD.