The type of memory that is non-volatile and retains data without power is flash memory. Unlike volatile memory types, such as RAM, flash memory maintains its data even when the device is turned off. This property makes it essential for storing firmware, operating systems, and user data in devices like USB drives, solid-state drives (SSDs), and memory cards. Flash memory is widely used due to its durability, speed of access, and ability to perform read and write operations quickly, making it ideal for a variety of applications.