"SD" stands for "Secure Digital," which is a type of memory card used for storing data in various electronic devices. These cards are commonly found in cameras, smartphones, and tablets, providing a portable way to save photos, videos, and other files. SD cards come in different sizes and capacities, allowing users to choose the right one for their needs. There are several types of SD cards, including SD, SDHC (Secure Digital High Capacity), and SDXC (Secure Digital eXtended Capacity). Each type has different storage limits, with SDXC cards supporting the largest capacities. These cards are widely used due to their convenience and compatibility with many devices.