A micro Secure Digital (microSD) memory card provides a cell phone or smartphone with expanded memory, allowing you to add more content, such as video, photos and music. As of June 2011, there are three types of microSD cards on the market that offer differing amounts of memory, each designed to fit the diverse needs of cell and smartphone users.
In addition to supporting added video, photo and music files, the expanded memory offered by a microSD card enables your phone to run more efficiently. Memory is the amount of space available for storing data and running applications. Each application on a cellphone or smartphone, such as digital camera, GPS or video game, requires a certain amount of memory to run properly. With larger amounts of memory, your phone has more room to store data and run applications, so they'll run more smoothly and experience less lag time. The amount of memory you require depends on the number and type of applications on your phone.
MicroSD cards come in three categories: standard microSD, high-capacity SD (SDHC) and extra-capacity SD (SDXC). MicroSDXC memory cards offer the most memory – 32 gigabytes (GB) to 2 terabytes (TB) – and are designed for large-scale, high-definition video recording, but are not currently supported by cellphones or smartphones. MicroSDHC cards, on the other hand, are designed specifically for cellphones, smartphones and digital cameras and provide 2GB to 32GB of memory. MicroSD cards offer less than 2GB of memory and are used in low-end and older cellphones.
All SD cards, including the micro-size versions, belong to two categories: Speed Class (SC) and Ultra-high Speed (UHS) Class. These refer to data transfer speeds in regard to video recording. The SC is broken down into four speed classes – 2, 4, 6 and 10 – which meet either normal or high-speed bus interfacing requirements. These classes, compliant with each micro SD card type, are ideal for the quality of video produced by a cellphone or smartphone’s recording capabilities. The UHSC, comprised of just one category – Class 1 – is designed to handle massive high-definition video, such as the type used for live broadcasts.
Distinguishing a microSD card from the other types of SD cards should be an easy task, given their size. At 0.4 inches wide, 0.6 inches long, 0.04 inches deep and 0.02 ounces, microSD cards -- the smallest of the SD card categories -- are about the size of a fingernail. SD cards are about the size of a postage stamp and miniSD cards are about 37 percent the size of an SD card. MicroSD cards are designed to give you the option of expanded memory in a compact package.