MO drives, or magneto-optical drives, are storage devices that use a combination of magnetic and optical technologies to read and write data. They typically use a laser to heat a small area of a magnetic disk, allowing the magnetic properties to be altered. This process enables data to be written and erased, making MO drives reusable. These drives are known for their durability and long data retention, often used for backup and archival purposes. While they have largely been replaced by other storage technologies like USB flash drives and solid-state drives, they still find niche applications in certain industries due to their reliability.