SD stands for "Secure Digital". SD is a type of memory card used to store data on portable electronic devices. Examples include digital cameras, video recorders, smartphones, and portable music players. It measures 24 x 32mm and 2.1mm thick. All cards have nine pins and a write protect switch. All flavors operate between 2.7 and 3.6 volts. Secure Digital (SD) card is a small flash memory card designed for high capacity memory and various portable devices, such as car navigation systems, cell phones, e-books, PDAs, smartphones, digital cameras , music players, digital video cameras and laptops. Memory cards are used to increase the storage capacity of cell phones, SLR cameras, dash cameras, drones, and other electronic products.