A disk drive is a device that reads information from and writes information to a spinning disk, letting computers store data even when they're turned off. Think of it like a tiny record player inside your computer: just as a record player uses a needle to read music grooves on a vinyl record, a disk drive uses a special reading head to access data stored magnetically on spinning metal platters.

For decades, disk drives (also called hard drives or hard disk drives) were the main way computers saved everything: your documents, photos, games, and the operating system itself. The disks inside spin incredibly fast, thousands of times per minute, while the reading head hovers just above the surface, closer than a human hair is thick.

Modern computers increasingly use solid-state drives instead, which have no moving parts and work more like giant memory chips. They're faster and more reliable, but disk drives still matter for storing huge amounts of data inexpensively. Data centers and backup systems rely on them because they can hold tremendous amounts of information at lower cost.

You might also hear about floppy disk drives, which were common in the 1980s and 1990s. These read flexible plastic disks that you could remove and carry around, though they held only tiny amounts of data compared to modern storage.