Head parking
Moving the read/write heads to a safe place before the disk stops, so they don't land on and scratch the data-bearing surface.
A hard-drive head floats fractions of a micrometre above the platter on a cushion of air that exists only while the disk spins. Slow it down without parking the head and the head drops onto the surface at full speed — a head crash that can scrape away both data and magnetic coating. Parking avoids that by getting the head clear first.
Older drives had a dedicated landing zone at the inner edge, a data-free ring where the head rested against the surface (contact start-stop). Modern drives instead lift the head fully onto a small load ramp at the edge, so head and surface never touch at rest. Laptop drives also park automatically when an accelerometer senses free fall.