M.2 PCIe NVMe Drives
These small, rectangular drives look like sticks of RAM, only smaller. They are usually 80mm long by 22mm wide, described as size 2280, but some may be shorter or longer, so make sure you get one that matches your slot. You can get M.2 drives that support SATA, but most modern desktops and laptops with M.2 slots support the faster PCIe NVMe standard.
You can get a SATA drive in the M.2 form factor, but most SATA drives are 2.5-inch models, which allows them to drop into the same bays that hold laptop hard drives. SATA drives are the cheapest and still the most popular choice amongst consumers.
While SAS drives look identical to SATA drives, they are very different technologies. The SAS interface can read and write at symmetrical speeds meaning that you can read and write at the same speeds. This interface is rarely found on consumer motherboards since it’s an interface mainly geared towards servers and workstation users.