An SD Card, or Secure Digital Card, is a small, portable storage device used to save and transfer data. Commonly found in devices like cameras, smartphones, and tablets, SD cards come in various sizes and storage capacities, ranging from a few gigabytes to several terabytes. They are designed to be easily inserted and removed, allowing users to expand their device's storage or transfer files between devices. SD cards use flash memory technology, which means they retain data even when not powered. They are available in different formats, including microSD, which is smaller and often used in mobile devices, and SDHC or SDXC, which offer higher storage capacities.