Learn in the textbookAuxiliary Storage and Flash Media — HDD, SSD, USB, SD
DefinitionAn SD card (SDカード) is a storage medium that packs flash memory into a thin, small card and goes into a device's card slot.
ExplanationDigital cameras, smartphones, and similar devices use it widely to record photos and video. It comes in different sizes, such as the smaller microSD, and in capacity-based standards such as SDHC and SDXC.
AnalogyIt took over the role that film played in film cameras: it records what you shoot, and you can take it out and move it to another device.
Memory hookSD stands for Secure Digital. The word Secure comes from its built-in copyright protection features.