Types of SSD Drives

SSD refers to Solid State Drive, which is a non-volatile NAND flash memory-based storage device.

SSDs are commonly used to replace hard drives as boot (system) drives and for primary data storage. Because there are no moving parts, a flash based drive can access data faster than a spinning hard drive. Camera and smartphone memory cards are also flash memory based, but use a much simpler controller, and are not as fast or reliable for storage as SSD drives. SSDs are more expensive per TB than large hard drives, so spinning hard drives are still useful for backup and for cost effective massive storage requirements.

There are several different types of SSD drive which differ in their physical packaging and their interface to the computer

Package: 2.5 inch drive Interface: SATA 6 Gbps or SATA 3 Gbps

Package: 2.5 inch drive, Interface: SAS 6 Gbps or SAS 12 Gbps

Package: M.2 Interface: SATA
Note that some motherboard M.2 sockets are dual-keyed and can take either NVME or SATA drives, some sockets are exclusively one or the other.

Package: M.2 Interface: PCI-e NVMe Generation 3 and Generation 4
Gen 4 slots are also backwards compatible with Gen 3 SSD drives.
A SATA M.2 socket will not take a PCI-e NVME drive. Some motherboards have dual-keyed sockets that will take either type.

Package: U.2 Interface: PCI-e NVMe

Package: Apple Proprietary Interface: ACHI

Package: Apple Proprietary Interface: PCI-e NVMe

Package: mSATA Interface: SATA

There have been other, proprietary packages from laptop manufacturers, which have died out