microSD - definition
SD stands for Secure Digital. MicroSD is the industry level's smallest memory card or flash storage. Back in 2005, it was invented by SanDisk. To use this storage device smart phones or specific handheld devices should have a MicroSD slot built-in. Otherwise; you can’t expand the storage of an iPhone using MicroSD. There are a few subsequent versions of it which are known as SDHC (High Capacity), SDXC (Extended Capacity).