Secure Digital (SD) is a type of memory card used for storing data in various electronic devices, such as cameras, smartphones, and tablets. Introduced in 1999, SD cards come in different sizes and capacities, allowing users to expand their device's storage easily. They are designed to be portable and durable, making them ideal for everyday use. There are several variations of Secure Digital cards, including SDHC (Secure Digital High Capacity) and SDXC (Secure Digital eXtended Capacity), which offer higher storage limits. These cards use flash memory technology, ensuring quick data access and transfer speeds, which is essential for tasks like capturing high-resolution photos and videos.