M.2 was developed by the PCI-SIG and SATA-IO standards organizations and is defined in the PCI-SIG M.2 and the SATA Rev. 3.2 specifications. It was originally called the Next Generation Form Factor (NGFF), and then formally renamed to M.2 in 2013. Many people still refer to M.2 as NGFF.
The M.2 small form factor applies to many add-in card types, such as Wi-Fi, Bluetooth, satellite navigation, Near Field Communication (NFC), digital radio, Wireless Gigabit Alliance (WiGig), Wireless WAN (WWAN), and Solid-State Drives (SSDs).
M.2 has a subset of specific form factors strictly for SSDs.