This document provides an introduction to the SanDisk Secure Digital (SD) Card, including its scope, models, features, specifications, interface description, protocols, and appendices. Key points covered include SD Card standards compliance, memory partitioning, read/write operations, data transfer rates, error management, wear leveling, sleep mode, and compatibility with SD and SPI modes. The document also provides product specifications, pin assignments, register descriptions, protocol details, timing diagrams, and other technical information about the SD Card.