A memory card is a flash memory data storage device used in a wide range of digital devices such as mobile phones, digital cameras, PDAs, music players, etc. They are small, rugged and offer high re-record ability.
There is a wide range of memory card formats. MicroSD (SD stands for "Secure Digital") and M2 (memory Stick Micro) are the smallest at the current time. The microSD format was originally called TransFlash or T-Flash.
MicroSD was introduced in 2005 and widely used in smartphones, tablets, and other handheld devices, microSD is electrically and software compatible with the full-size SD card. Subsequent versions, including SDHC (High Capacity) and SDXC (Extended Capacity), greatly increased storage. Weighing less than one gram, 1TB SDXC cards became available in 2019.
In 2019, microSD Express cards debuted. Like full-size SD Express cards, microSD Express uses the PCI Express (PCIe) bus and provides a huge speed increase to as much as 985 MB/sec. For example, a file in a microSD Express card can transfer nearly five times faster than a UHS-I microSD card (see SD card classes). See SD Express, SD card, SD card classes and gruvi card.